as far as I can tell Marshall only ever used these on the solid state bass stuff they made in the late 1980’s these were also used on the jubilee bass series heads (the 3530 and the 3560)

These push on so can only be used on splined shafts

You can of course use them on other Marshall amps, ie a jcm800 or jcm900 etc 

have 9 of these in total Feel free to buy as many as you need!

Gold dust if your amp is missing or has mismatched knobs!