Quoted from DirtFlipper:

Most the of the Gottlieb schematics do not call out the flasher bulbs. Some do, but that's the exception.
Instead, the bulb socket itself is the indicator. Most of the sockets on the backbox panel are recessed. The original 44s have straight edges, so the bayonet bases and part of the bulbs can fit sub-flush with the surrounding wood surface.
The sockets that are intended to have the flasher bulbs (455s) sit flush with the wood surface instead. The 455s have a large 'globe' style glass, so the bulb part can't go sub-flush like the 44s (and 47s) can.
The Game Over socket is a pretty safe bet to be a flasher. Look at that socket compared to the others and the difference can be seen. But on the schematic the Game Over light isn't indicated as being a 'flasher' (usually).