In 1965, Why Did America Start Making Clad Coins Instead Of Solid Base Metal?

Of those desired five characteristics, only number 3, ease of production, supports clad vs the then-existing solid alloy. The alloy of the nickel is harder than clad composition, and thus more difficult to strike into coins. However, that difference also means clad wears faster than the nickel's alloy, which runs counter to desired characteristic number 2. So, Sap's question remains.

I believe that the technology of the 60's used induced electrical eddy currents to determine authenticity. For some reason the thin cladding mimicked the same effect in 90% silver.

The mint blamed everyone but the real culprits for the coin shortage.

It was really caused by millions of the general public hoarding silver. in the process they kept more than normal amount of cents and nickels. This rectified itself quickly as the hoarders released the small change so production of cents and nickels dropped sharply after 1964. It was the mint news releases starting in 1962 that warned silver prices were soaring and silver stocks were plummeting that caused the hoarding. Collectors were punished and the coin market was severely damaged as a response. Modern coins have never recovered from mint, FED, and congressional actions in '64 and '65.

That's a very different discussion than "How did we specifically pick clad for coins in 1965 instead of solid or plated coins?"

Fiat exists by declared consensus. While the paper may seem arbitrary, that medium of exchange is reinforced by the fact that if you make your own paper with 100 on it, government law enforcement officers with automatic weapons will kick in your door and drag you off to jail. There are lots and lots and lots of other features of civilized society that are exactly the same way. Arbitrary, but collectively agreed upon, and therefore enforced by steel and lead.

There are other factors that affected the decision to produce clads. Incredibly enough even though this is a government operation "efficiency" was one of those reasons. In those days it wasn't nearly as uncommon! The outer clad layer is 75 cu 25 ni so retired nickels could be used to make clads and the clads could be melted and mixed with nickel to make nickels. In those days Olin Brass made a lot of the clad planchets.

Okay, I think I've figured it out.

Here's a picture of a typical eddy-current discriminator, as used in 1960s vending machines (taken from the appendices in the BMI report):



Coins roll down the ramp and past a permanent magnet (another magnet earlier in the mechanism has already filtered out steel slugs and other ferromagnetic things that would actually stick to a magnet). The permanent magnet induces eddy current braking, slowing the coin down. Silver coins, with high conductivity, slow down a lot, and drop straight down after passing the magnet into the "good" bucket. Coins made of low conductivity materials barely slow down at all, carry on by inertia, and overshoot the "good" bucket; they land in the "slug" bucket instead.

The core of clad coinage is 100% pure copper. This is important, because pure copper is a much better conductor than pretty much any copper alloy, or anything else except silver. For example, cupronickel is 20 times worse at conducting than silver, while pure copper is only 3% lower than silver.

So a pure copper coin - or a coin with a pure copper core - isn't "as good as" silver in this test, since that would be against the laws of physics - but it doesn't need to be "as good as" - it only needs to be "good enough" to fall into the correct bucket. The lighter weight of the clad coins confused me (and the Report indicated the new coins would have to be be lighter in weight, without really explaining why), but the lighter weight is actually necessary for the deception to work: a lighter coin has less inertia, so is slowed down more by the magnet and won't travel as far. You need the combination of pure copper core and lighter weight to trick the mechanism into accepting a clad coin.

There were three manufacturers of eddy current vending machines in America at the time. BMI presumably tested all three machines, and found all three were reliably fooled by clad coin blanks.

So it seems "vending machine compatibility" is indeed the answer to the problem. The vending machine industry in other countries that got rid of silver at the same time (eg. Australia) was smaller, and most of the machines there apparently didn't use eddy current discriminators, only diameter/weight detectors, so cupronickel coins that were the same size and weighed the same worked just fine as a substitute. The few vending machine operators who used US-made vending machines that did use eddy current discriminators, and needed to adjust their machines to work with the new coins, were monetarily compensated by the Australian government - something the US government couldn't possibly have afforded to do, given the size of the vending industry there.

Cupronickel is essentially transparent to the eddy tester, so the cladding is irrelevant, in terms of what it contributes to the overall eddy current response of the coin. But it does add two important things to the coin beyond passing the eddy current tester: size, and colour.

Size: prior to the eddy current tester, the coins are filtered by size as well as weight. The cladding is essentially "padding" for this test, bulking the coin out to make the coin a passable size and thickness without making the eddy response either better or worse. They could probably have used a plastic coating with much the same effect.

Colour: cladding makes the coins "look silvery", which was believed to be of paramount importance. A 100% pure copper solid coin (no cladding) would have been preferable to a clad coin, for the eddy tester, but pure copper is (a) too soft for heavy circulation, and (b) "too cheap-looking". Likewise, a thin plating of silvery metal over a copper core was rejected because the copper would still be soft and quickly wear down, and the thin layer would wear away too quickly, exposing the copper core. Cladding applies a thick enough layer to prevent this, even after heavy circulation - as everyone experienced with heavily circulated clad coins can attest.

Yes, brandmeister, the alloy of the Sac dollar is specifically tailored to give the same response as the clad composition of the Anthony dollar. That's the reason it contains manganese, which causes it to turn black in circulation, just the way the Cu-Ag-Mn " War Nickels" turned black.

The SBA dollar, in turn, is NOT made of the same clad composition as other US clad coins! The materials are the same, but the layer thicknesses are different. That was so that one couldn't chuck up a half-dollar in a lathe and turn it down to dollar-size, and have it pass a vending machine discriminator. Frankly I regard this as stupidity. They could have used aluminium-bronze or something like that for the outer layers (and made it actually polygonal to boot), and it would have been accepted by people much better.

And nick10, that answers your question too. For each individual denomination, there's a bucket. The balance of weight and retardation (that means slowing-down) is unique for each coin. Nickels go in the nickel bucket. Other coins made of the same alloy, at the same diameter and weight, will go in the nickel bucket. Coins made of the same alloy, of different weight and diameter, will not.

The key with roll-clad material is that you can make the electromagnetic properties effectively arbitrary. One of the few countries other than the USA to use Cu-Ni/Cu clad is Thailand. If you look at the Thai clad coins, they have a much thicker copper centre, so the balance of properties is different.

As BStrauss3 mentioned (hi!), I have a German payphone made circa 1990, which has a very sophisticated coin mechanism. It has to accept 10 pf coins which are made of plated steel, and therefore strongly ferromagnetic (remember that US coin mechanisms normally just reject or trap any ferromagnetic object) ; 50 pf and 1 DM coins which are cupronickel, non-ferromagnetic ; and 2 DM and 5 DM coins which are made of "Magnimat", a clad material with a pure nickel core (ferromagnetic) and cupronickel outer laminations, giving it a unique signature. The Swedes (1 and 5 kr) and apparently the Portuguese (10$00) also used this material in the '70s.

The thing is, even this very sophisticated, computer-controlled mechanism can be fooled into accepting much less valuable coins in place of the 1 DM. They're about the right weight and size, and made of the right material. Some off-spec coins work too, because they are wrong one way in a way that offsets being wrong in another way. You can read about my experiments with that, here.