The area around that socket doesn't look like it was doused with mouse pee. It's hard to imagine any other way to get that socket really wet. The chassis as found was quite dusty, but with no serious rust or signs of moisture damage.
The socket phenolic looks somewhat burned from the top.
This socket's chassis opening is larger than needed for a 7-pin tube. The chassis hole is 1" in diameter and the mounting centers are 1-5/16". It's as if the chassis previously had a standard octal tube in that position and they changed to a 7-pin tube and got wafer sockets to fit the same hole.
I've been looking at the usual sources (Surplus Sales of Nebraska, eBay, Antique Electronic Supply), and nobody seems to have a 7-pin socket that fits.
Does anybody know of another source?
Phil Nelson