I agree with GB that hand held XRF’s are the best way to test alloys. The problem at least in San Diego sized cities is finding someone with one of these devices who would do the test inexpensively.
I think that 2152's method might be the best alternative approach for steel and I'll try this method next time. Thanks.
I also took the course on CCH at Lassen College and CCH'ed an Italian made Remington rolling block action. I ground off a small spot on the bottom of the action and used the schools hardness tester to check the action's hardness. The hard top surface was less than .010" deep and the rest of the action wasn't hardened. 
However, several test pieces, using pre WW-2 M-98 magazine floor-plates, thought to be made with low carbon steel, were through hardened and brittle. This has led me to file test any thin CCH'ed parts.
Otto