Is this a polished stainless steel gun or a polished blue steel gun? The stainless steel gun will resist rust and can get hand polished to remove any small amount of rust that might appear. Blue steel will need to have the rust removed and reblued. As for threaded barrels, I just ordered and had fitted a threaded barrel match grade barrel for my P01 SDP model from Barsto Barrels. Contact them if you want a threaded barrel and can't locate one. I called and talked to them about what I wanted and they were very helpful and friendly to talk with. They include thread protectors in the price for their threaded barrels.
Link below or call them for specific information at (605) 720-4000.
Link to Barsto Barrels
Link below or call them for specific information at (605) 720-4000.
Link to Barsto Barrels