I really was dense this morning, it was about midday when I suddenly realized what you were saying. In the meantime, some guys on another forum gave me a great way to check them:
Metals have specific densities
Ti = 4.54 g/ml (for the most common Ti alloys)
Al = 2.7 g/mL,
steel= 7.85 g/mL
So, I can find out how many mL of metal I have by seeing how much water they displace when I submerge them. Then I can weigh them and calculate their density. I should them be able to get a warm fuzzy as to what they are. There is enough difference in the given values that I don't even have to be super accurate to get in the ball park. Of course this won't tell me if they are good US Ti or if they are from Russia or China.
I have asked the guy straight out if they are Comp retainers or not and if they are not, if he knows where they come from. We'll see how it turns out.
Thanks,
Lynn