Search:

Missing part is locking knob w/ 4-48 left hand thread. That is why virtually ever one i've see is missing.
natural tightening (RH) spins the knob out of the sight. Must be a few buried at ranges...

You have a Indian (east) military Mk III, meuphamistically referred to a "Curry Gun" by the wags on the Ross rifle site. There is a very good discussin on the site by BarryJ on the subject.
I have...

Zemeinc:
Military extractor will work just fine, but unless yours is broken it should extract. Try removal and bending in the head end and then try again.
If you have a proof stamp on the extractor...

I have been shooting Rosses for 50 years and never had a problem vis-a vis safety. If you diligently work at it hard enough you can get the bolt head reversed in a MkIII or an M-10 Then if you ram...