David. The pictures above posted by Roger are from a S/A box (top) and the earlier Plunger design (bottom picture). These ran side by side with the introduction of the S/A models until the phasing out of the plunger bikes, so here it's the model that's important rather than the year.
The greatest contrast is in the gear selector mechanism, the outer covers are characteristically different to reflect this and do not interchange. Nor do the gaskets, though similar all the castings are different. Plunger picture shows the inner shaft bush still on the kickstart shaft. This should remain firmly pressed into the inner cover casting. Compare this with the top picture.
The good news is that on standard boxes some of the internals are common to a degree, the oilseal, bushes, bearings and some of the gears but here again minor changes took place over time. Well worth researching the Gearbox Section of the Forum. Mis- matching Kickstart ratchets and quadrant types have baffled a good few folks. Pattern Part Suppliers don't always get it right, as you will find from previous threads.
Careful scrutiny of the S/A quadrant shows it to have "Pointy Teeth" The Plunger box is this case has flat topped teeth. The kickstart ratchet teeth come as flat topped or pointy, and the type must be selected to match the quadrant teeth. So now you know. But of course after numerous owners and 60 plus years later, never accept all is as it should be. Also is there anything amiss to cause the spring to fail?
Swarfy.
