I have a Winchester Mdl 363 pistol, which is a rebadged Diana 6. I bought it new in about 1970, and of course it needs seals, which I have ordered (from JM I think.) Thanks to a question on this forum from a month ago about a source for springs for Dianas, I found the Chambers site, which has a nice exploded view of the pistol with part numbers. At the rear of the pistol is a screw on End Cap, and right in front of, or inside of, the cap are a seal and a metal washer. On the Chambers site, they are labeled N/A for part numbers. When I took the pistol apart, I was able to extract the metal washer, but the other thing was completely deteriorated, and came out in chunks. the question is: What do I replace it with?" Does it glue the metal washer in place? I think that it has the function of acting as a bumper or shock absorper for the rear piston. Is the thickness critical? Would the gun shoot allright if I left it out? (Left over parts doesn't seem like the best answer for a restoration.)