Most of us probably go by visual feel, past knowledge of older known counterfeits, obvious weight, specific gravity/metal content and the good 'ole ring on a hard surface, but the Chinese fakes out there are so good that it is hard to tell how old the coins really are. [There must be a 'fake coin cartel' out there ruining the hobby for all.]
Anyway, for the next Whitman Baltimore Show, I'll plan to bring some interesting counterfeits from my own collection across the Bust, Liberty Seated and Barber series to share with Jim and others if interested. Maybe we could come to an informal consensus on the topic of fakes difficult to determine age (modern vs. contemporary)?
Just an idea...