Hey Cliff..
I asked this very same question of my teacher MS Wally Hayes and was told thats it's usually not worth the time in playing around with different unknowns... Either find or buy specific steel, which you know what it is, then there is no guess work..
I guess that takes the fun out scrounging for steel to use,, however if it's knives you want to make,, it will save you time, money, energy and resources making knives you aren't sure of.
I couldn't argue with that...
ttyle
Eric
O/ST