This is just like a home tester. Just have dig it out and put the batteries back in. The Whites 6000DI might be able to get a read on the metal content. The minelab gold monster 1000 will tell me if it's non ferrous metal.
The one with the white gunk is a standard corroded cent. Stay tuned for the weight and metal composition if my High tech tools still have good batteries Caliper measurement 18.88mm Minelab gold monster 1000 reads Non Ferrous metal 100% Whites 6000DI meter picture says it's gold well something else in that range. Hmmm, Now a Visual inspection with the EyeCrometer Not sure which would be the Obverse or Reverse.
Weight 2.038 gram. Google search has Possible coins with a diameter of 18.88mm narrowed down to include: Medieval English silver penny: A silver penny minted in London during the reign of Henry III (1216–1272) has been documented with a diameter of 18.88mm. A medieval short cross silver penny from the reign of King John (1199–1216), minted in Canterbury, also measured 18.88mm. These coins are often referred to as "sterling" silver pennies, as the term originated around that period. Roman silver denarius: A silver denarius of Domitian (reigned 98–117 AD) and a Hadrian denarius (128 AD) have both been recorded with a diameter of 18.88mm. Roman silver coins, while not sterling, were a common currency for hundreds of years. Indian Princely States silver rupee: A silver rupee from the Gwalior State, minted in the name of Jankoji Rao, has been recorded with a diameter of 18.88mm. Ancient Greek silver coin: An authentic ancient Greek silver coin has been sold on eBay with a listed diameter of 18.88mm. Mexican silver 20 centavos: A 1937 silver 20 centavos coin from Mexico was documented with a diameter of 18.88mm. Lithuanian silver 1 litas: A silver 1 litas coin from 1925 has been noted with a diameter of approximately 18.88mm. Google suggests To narrow down the possibilities, you will need more information about the coin, such as: Its country of origin NOPE Any text or markings on the coin NOPE The image or figure on the coin NOPE The year it was minted NOPE
At that weight and size, I'd guess it's a Zincoln core. I can think of a couple of tests to do on it, but they're kind of destructive.