My thoughts on the evolution, er, or should I say de-evolution of this dagger is:
Early- Silver with steel based scabbard.
Mid-Period- "Aluminum" plated scabbard, as Wotan suggests. (BTW Wotan I have never seen an aluminum scabbard based RR with a screw securing the throat, so I agree with your reply above.
Late- Finally solid aluminum scabbard with a formed throat.

Vesuvio, I can make no judgement based on what I see. I do not like looking at a single component and making a call. Can we see the whole thing? From the scabbard alone, the finish looks rough, maybe replated, or wire brushed? The original finish was either a brushed aluminum look,(like Pat's) or early silver washed. Compare the scabbard tip to Pat's, your's is far "blunter". What are your liners made of?