Ancient Unknown 'Key' Coin?

The key shape is a winged caduceus. See this link:

https://www.vcoins.com/en/stores/ro...Default.aspx

I do have concerns about the coloring or plating (painting?) of yours. It should be silver.

Well, my fear is that it might be a cast fake, painted or gold leafed or whatever to fool a tourist who doesn't know that the coin should be silver.

Let's see what others say.

I don't know if this changes anything but its weight is 3.1 g.

Also, how could I test it to determine if it is silver(Ag)?

Two issues here, for future reference.

First, ancient coins are hand-made and are much more prone to errors than modern coins. Unless an "error" is spectacular (such as mis-spelling the emperor's name) it usually does not attract much if any premium. It is the perfect, error-free examples that usually command a premium.

Second, ancient coins don't "delaminate" like modern ones can. Modern coin blanks are made from large slabs of raw metal that have been rolled and rerolled flat by huge mechanical presses; it is this process that stretches the metal out and causes laminar features and errors. The blanks are then punched out of the metal sheet by an equally huge machine. They simply didn't have machines capable of doing these things back then. Ancient coin blanks were usually individually cast.