[GrayHair]

I saw knobs secured with set screws or thru-pins, but that type of shoulder on the spindle is new to me. Makes me think it might be a press-fit (unlikely) or glued in place (measured amount of glue/epoxy in a blind hole).

 

[GrayHair]

Split spindles are used to lock the "outside" knob while leaving the inside knob free to retract the latch. Usually used on exterior doors, not on passage or privacy sets.

As for reproductions, I don't see the wear I would expect on the ferrules or setscrew, hub wear on the spindle or the chipping or crazing normally seen on old glass knobs. Rings do a lot of damage to glass knobs over time. The house may be old, but the knobs/spindles could be much newer.

EDIT: The metal under the brass was usually pot metal which is very soft compared to the steel of the spindle. Consequently, not a good choice far a long-lasting press fit.

 

[GrayHair]

A picture is worth 989 words, while a new thread, where people don't have to wade through all the previous posts, is worth 2000. Explain your problem there.