b310gx, could you help me identify what the gearboxes I have are and where they might have come from.

I have 3 gearboxes sitting on my shed floor at the moment. 2 have 56A stamped on the bellhousing with drain plugs at the bottom facing backwards. One has what looks like a second reverse switch?? Its located just below and back from the clutch fork (cable clutch). I assume these are standard Datsun 1200 4 speed boxes. They do look slightly different from each other as one is smooth on the outside and one has casting web/ribs on the outside.

The other box has nothing stamped on it anywhere. Exept for two small number 8's on the top of the actual gearbox part on either side of a web/rib. It has (A) 2306535 stamped on the very top flat part of the bellhousing where it bolts to the motor. It has the reverse switch on the side.
The thing I cant understand is the gear lever will move up to where 5th would be (normal shift pattern). I doubt this is a 5spd box, could my reverse gear be stuffed and it somehow allows me to shift up to 5th (above reverse).

Thanks for any help