[jeffbee]

Interesting. A student horn I guess? I've never owned one that didn't have at least a third valve slide ring. I think they were widespread around the time that the trumpet really took over from the cornet, around 1900-1920. My pre-War Olds has moving slides.

[bluGill]

I know a few cases where slides were added later. I don't know when they became common but impression is layer.