Determining A Coins Authenticity By Measuring Its Conductivity

JohnZ

This is a liteside question that comes from the darkside. The Nordic Gold alloy, developed in Sweden, and used in Euros and other coins is engineered with a very specific conductivity that can be measured by vending machines to determine the coins authenticity. I imagine a current of specific voltage is passed through the coin, and the resultant drop in voltage can ascertain the resistance (in ohms) of the metal. An improper alloy mix would result in an improper resistance.

Has anyone ever heard of such a thing in US coins?

ClausUrch

Jeez...We can't even get our vending machines to accept half dollar or dollar coins let alone some high tech way of authenticating what has been inserted. This concept would go over like a turd in a punch bowl with the US vending machine lobby!

Shamika

"This concept would go over like a turd in a punch bowl with the US vending machine lobby!"

I'd say that sounds about right.

XpipedreamR

When they were coming up with the new alloy for the Sac. dollar, I seem to remember that one of the considerations was matching the electrical conductivity of coins already in circulation so that it could be used in vending machines. So, they may already do this in some machines. Or maybe my mind is playing tricks on me and I'm imagining the whole thing!

cladking

XPipedreameR has it right. Vending machines already use the electrical characteristics
of coins in their discriminators. I believe this is primarily resistence but don't know. This
applies to all the more sohisticated vending machines. Laundry machines and gum ball
machines generally have very primitive discriminators. Toll roads usually have very good
discriminators but they can be adjusted so they don't back up traffic during congested
periods. A person who unknowingly tosses in a Canadian quarter will sometimes just sit
and honk rather than put more money in.

When the clads first came out it was often a while until all the machines would accept them.
Over the years though the machines have been adjusted and now only accept coins in a
very narrow range. This means that silver and improperly cladded coins will not work. When-
ever I see someone have a coin returned I offer a "good" quarter in exchange.