One is to rub it with your fingers until it's warm then smell for a formaldehyde type smell. A similar way is to run it under hot water and check for the same smell. Not all piece will test positive to either of these, because of the amount of bakelite or pheno...something in the piece (can't remember the name...been a few years)

The other tests are with 409, scrubby bubbles, or simichrome polish. Use a q-tip and rub any of these particular products on a chip. If the q-tip turnd yellow, it's bakelite. Any other color and it's probably not. Wipe off the 409 or scrubby bubbles. rub in the simichrome.

None of these are fool-proof.