What year did weihrauch change to synthetic piston seals?

[zrman27500]

Interesting. Is it stamped R7? Is the serial number on the barrel? If so, I wonder if Weihrauch had some NOS barrels when they put that R7 together in 83.

Correct,it is stamped san Rafael beeman,serial on the underside of barrel.rifle appears to be all original, I'll post serial # later when I get home.