File marks on the blade would not be unusual. It was not the practice to always bring a blade to a high polish, and often rough file or grinding marks are seen. You could leave them, or polish them out. Neither would be "unauthentic," but polishing them out would be changing the original state of the blade,
I would be interested in some close-ups to. It does not look like the sort of blade that would have gold koftgari, though. It is most often silver, sometimes with some copper details. Have you tried cleaning it with a solvent like paint thinner? It might be a yellow discoloration of a varnish or other coating on the blade. Then again, it might be gold.
