Hello all, first timer with a question. I recently purchased an lee Enfield in unissued condition. Brought it home and cleaned it with hoppes solvent and then wiped off and applied oil. I put it in the case a couple weeks ago and when I took it out to show my father I noticed it now had brown marks on the rear sight and on the serial number on the bolt was turning brown. Is this rust and I missed a spot? How do I remove it without ruining the perfect finish especially on the small numbers of the serial number.