Thursday, July 10, 2014

7/10/14 Report - The Math of Metal Detecting and How It Can Assist Decisions and Strategies

Written by the TreasureGuide for the exclusive use of

Old Class Ring Found With Metal Detector
Source: Online

This is one of those class rings that was lost for a good number of years, but was recently found and returned.  I'll post the source of the article and photo if I can find it again.

Today I want to talk a little about the math of metal detecting, especially as it affects the strategies you might use.  This discussion will of necessity be very general because there are simply too many factors that can affect your results, and I won't be able to get real specific in this one post.   Each person's situation differs in a variety of ways.  Therefore this discussion should not be considered precise or final in any way, but it should help you to think about how you hunt and different decision strategies that you might use.

I have more reasons than one for presenting this topic.  You might decide to modify your detecting strategies as a result of this discussion.

If I remember correctly, the average face value of clad coin finds is about 7.5 cents.  That number should be close enough for this discussion anyway. 

Many things can affect that average for you.  Maybe you discriminate out nickels, for example.  Maybe you discriminate out zinc pennies, or maybe your detector is more or less sensitive to certain denominations.  Or maybe it is where you hunt or how you hunt that makes the difference. 

I'm sure some locations will produce proportions of different denomination coins than others.  For example, if there is a parking or entrance fee that is something like $2.50 cents, the number of quarters you'll find will probably be higher.  People will get often get fifty cents back in change.  That will increase the number of quarters and the average face value of coin finds.

All things considered, for discussion purposes I'll adopt 7.5 cents as the average face value for clad coin finds.

Using that number, if you want to pay for your a detector that cost you $1000, you'd have to find over 13,000 coins to pay for it that way.   Of course, that doesn't include any other items of value you might find, but that is a lot of coins.  You would be doing very well indeed to find that many coins in a year. 

If you find one Rolex (lets say a Rolex that you could sell used for $15,000, which is not the highest or the lowest) that is worth something like over 200,000 clad coins.  

Here is one thing I want you to see.  If you find one Rolex like that, the value would be higher than the value of coins that you might find for a period of several years.

So what would you rather do, dig a couple hundred thousand coins or a Rolex?

If people want to dig a couple hundred thousand coins, that must be the reason they air test their detector with clad coins.  Right? 

And that must be the reason they always talk about how deep they can detect a coin.  Right?

For me, the economic value of clad coins is not a lot better than what you could get for a bucket full of aluminum pull tabs or the lead from a bunch of sinkers.

If you'd rather find a Rolex than clad coins, or if you'd rather find gold rings, as another example,  adjust how you do things.  Air test your detector using the kind of things you really want to find.  Do your tests and practice with the kinds of things you want to find.   Again, I don't much care how deep a detector will detect a clad coin.  That is not my primary target.

If you would like to find a Rolex watch, practice running your coil over watches and see how they sound.  And go where Rolex's can be found. 

There are some places where it is much less likely that you will ever find a Rolex.   I'm just using the Rolex as an example, but I'm really talking about deciding whatever it is you really want to find and adjusting your behavior and strategies. 

If you want to find gold rings you might consider air testing with a gold ring instead of a coin, and setting your detector's settings to maximize the response to those types of targets instead of clad coins.

Of course there are many things that have a value between clad coins and a Rolex.   There are rings of various sizes and values, and all kinds of other things.

Below is a little chart I made.  The vertical axis shows the frequency of different types of finds, going from common inexpensive finds at the top to less common and higher value finds at the bottom.  The horizontal axis shows the value of different types of finds, going from one cent on the left to $100,000 on the right.

To the left of the curved line is worthless junk. 

The line starts high on the left because very low value targets are very common and very frequently found.  Hunting like most people, you'll find many pennies, nickels, dimes, etc. and not as many gold items.  

As the value increases (line going from left to right) the frequency they are found generally decreases (line goes from high to low).

Just to the right of the beginning of the downward sloping line there is a curve as you get into targets of increasing value such as silver rings, small gold rings, better rings, etc.   

Silver rings and gold bands fall largely in this big curve area.  They are less common than coins, but more common than more valuable finds.

The line gets pretty flat way out to the right.  There is not much difference in the probability of finding a $30,000 ring or a $40,000 ring.  That is why the line gets flat.  The frequency (or probability) does not decrease much at the very high level.  They are all fairly rare at that level.  How rare depends to some extent on where you hunt.

Lets say you find a gold band weighing one tenth of  a troy oz.  That is not the smallest you could find and it is way smaller than the heaviest you could find.  I would say it is not an uncommon weight.  You might get $60 or more for one tenth of an oz. of 14K gold at today's prices.  A ring like that would be worth something like 800 clad coin finds.

Of course you could find a ring weighing a full oz. or more, or it might have good quality diamonds, taking you up in the tens of thousands of dollars.

Low value targets are very common, but it seemingly takes forever for the value to accumulate to anything very significant.   Therefore, when deciding what you want to target you might want to make a calculated decision about where and how you want to hunt.  Maybe an area that produces fewer coins but more high value targets would be worthwhile.

You have to remember that low value targets have value other than economic value though.  For example, they can be signs or indicators about how the beach is sifting and sorting items.  That is an entire additional topic.   They also have a psychological value for some people because they at least keep it interesting when the hunt for higher value targets drags on.  Some people need the low value finds to keep them interested between higher value targets.  Not everybody can tolerate long periods of finding very little.

For me the "sign" or "indicator" value of coins is by far the most important.  In that regard they are again very much like pull tabs and types of metallic junk.  They tell you something about how the beach is sifting and sorting, and therefore also something about where you will or will not find the gold.

Economically, clad coins aren't worth a great deal more than the aluminum in a bucket of pulltabs or the lead in a bucket of sinkers.  

I'm not talking here about coins that have a value beyond their face value.

Here is a main point.  People often behave and detect in a way that would suggest that what they most want to find is clad coins.  

When you figure out which sites are best, don't forget to figure in the probability of large value finds.  At some locations the probability of a large value find might be near zero.  At locations where they are possible but not likely, don't entirely discount them because when they do occur the value is soooo much more significant that it will really make a difference in your totals.

I think a lot of people figure that if they go out and meander around and find some coins eventually they'll get a ring or something better, but if you want to maximize the economic value of your finds, you need to figure in the probability of higher value finds, which will affect your totals much more than clad coins. 

As I attempted to show with the calculations above, it takes relatively few high value finds to drastically change the total value of your finds.  Don't under weight high-value finds when you decide where and how you are going to hunt.  I'd rather hunt locations where I can target higher value finds.   One or two of those quickly adds up to more than many low value finds. 

If you intentionally target high-value finds, you will not necessarily find much else.  Some places have a good mix of coins and gold.  Sometimes there is a lot of gold where there are a lot of coins.  And at some places there are good high-value finds such as gold but almost no coins.  At first it might seem like that type of location holds nothing.   There might only be a few targets, but it only takes one high-value find to make a good day.

Condominium beaches are not like park beaches, for example.  People in condominiums normally don't fill their pockets with coins before going out to the beach.  Whereas people who have to put money in meters or pay an entrance fee or buy hot dogs, will have and lose more coins, but not necessarily good jewelry.

I am encouraging you to be specific about what you target.  Sample different locations.  Make some observations.   Collect data.  Make decisions more methodically, and hunt strategically.

Back to the economics of the issue.  Lets say there is a good chance of getting a $10,000 find at one location, and a good chance of getting a plain gold band of around one tenth an ounce ($60) at another location about once in every five hunts.  Your estimate might be that you would hit a quality ring of about $10,000 value once in 20 hunts and at the other location a gold band once every other hunt.  You'll find gold more often at the second beach, but look at how that works out. 

Expected value per hunt at the location with the probable high value ring = 1/20 x 10,000 = $500.
Expected value per hunt at the location with the probable gold band = 1/5 x $60 = $20.

Even though it might take much longer to hit a high quality ring at one location, it would average out to way more value than lower quality rings at another location even though on average you find them 4 times as often.

You can't evaluate a location based upon a single item, but you can see from this analysis how a piece of gold can heavily influence your average expected value at a site - certainly much more than common coins.   Figure other significant items in to the analysis as appropriate.

A site yielding a fair number of heavy class rings might produce a higher average value than a site producing a lot of wedding bands. 

Again, there are too many factors for me to address them all now.

I'll wind this up.  Here are some of my main points.   Be clear about what you target and why.  Adjust your decisions and strategies according to your target.  Be aware of the trade-offs.  Select sites based upon your best data and estimates and don't underestimate the value of high value targets.

Well that took a while.  I still had to really cut things down to make it semi-understandable.

That is as much as I'll get into today.

On the Treasure Coast the surf is still small but the tides are increasing a little. 

Happy hunting,