You could try a backyard archival test Mike. Use the fixer on a print and a roll of film. The dilution factor for the film is probably in the ballpark of other paper developers. Then hang a neg strip and the print outside, next to a neg strip and print from your previous fixer. Just see what happens over a period of time and weather conditions.
But I'd sell the fixer, and put the money toward purchasing new film and paper fixers. It's just not worth the risk.
But I'd sell the fixer, and put the money toward purchasing new film and paper fixers. It's just not worth the risk.