Quote from: EnzoProbably RCA 40409 and 40410 types.
I agree, but with one reservation. These transistors also had downward lugs to attach the heatsink portion to the board, and I don't see matching holes in the board for these lugs, but it certainly looks like somebody intended the drivers to have heatsinks that aren't there.
I'd approach this one with considerable caution and suspicion because it looks like it has been badly messed about at some stage in its long life. Until you get it going you are going to need to be in constant reality-check mode.
Here is an account of my own bruising encounter with a messed about Gibson amp.