Model 1898 and model 1899 Kragicon receivers use the Magazine Cut-Off Lever with the short shaft.

I have been seeing cut-down Krags at gun shows for ages with that "Curtain Rod Fixture" front-sight. I don't know who made them. They are hideous and make me cringe.

I suspect they were a hardware store (non-gun) item, that got improvised into a 'gun-sight'.

They were probably driven on and held in place by friction. They are common.