I would be really really really careful about those... good 'drivers are well hardened and tempered. Those ones are.... "suspect until proven otherwise".
Hate to see one twist when you apply torque. Again, if you are not really torquing them... they might be just dandy.
Read up on how to harden and temper screwdrivers with a torch and some oil too... might be able to make these into decent tools depending on the steel that's in them. You can estimate carbon content by looking at the sparks thrown by a grinding wheel. I'm sure that there are internet articles on this. Roy Dunlap's book "Gunsmithing" has been my life-long reference work, if you can pick up a copy.