Plunger frame axles ?

This may be wishful thinking, but does anyone know why Norton plunger framed ES2 and Model 7 axles have different part numbers,
and how the axles are different ?



My interest is that I have such project bikes, and parts that may or may not be genuine,
but the differences are not obvious - and they seem to interchangeably fit.
While they are different, the spacers make them up to be the same ?
Is there something that I am missing, or are these parts not what they seem to be ?

The difference between the two is obvious (overall length of center section and spacers on both sides). How they MIGHT be able to be interchanged most likely depends on the hub, bearings and other components that need to co-exist.

Yes, but I don't know if thats how they were made, or if thats how they are configured now....
What would be good is if someone with these models can measure the various bits on their axles.
Or just photo their setup.

The hubs, drums, spacers and axles all seem to have different part numbers.
But the width between the plunger rear suspension units / alloy axle housings is identical.