Corbin skeleton keys-different series?

[Pschiffe]

I guess I'm still confused as to what the "B" means stamped on them before the "Q". The person selling them has no idea either. Bit, maybe?

I'm guessing BQ and Q are probably different series, but; maybe buy a couple and give them a try, perhaps BQ 4 = Q 4? The Q Series is very uncommon, but I have seen them. The P1- P12, R1 - R72, BQ1- BQ250 and BT1 - BT48 are the more common series of P & F Corbin bit keys, all of which were available as pre-cuts back in the day.

Pete Schifferli