Pretty sure it is a coin weight, used to measure against authentic coins of the time. It means 2 penny weights and 16 grains. That's what the P and the G stands for...I think. Most probably british and Georgian
It's not a weight - a weight would actually say exactly what it weighed, rather than leave you guessing.
It's a token. Who or what "P.G." is, may be difficult to determine. In many places around the world at various times, gambling with actual money was/is illegal, so people make tokens to gamble with instead; in such cases, the people making the tokens are acting in secret, so obtaining information of who, how and when the tokens were issued is next to impossible, without "inside knowledge".
The OP is from Italy. If they found it there, then it's probably local in origin, and "P.G." would then be an Italian abbreviation.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis