No not this Model Engineer, the one run by David Carpenter.
Listed in the index at MEWeb is an article on PTFE valve rings, but if I click on it I get a message saying page cannot be found. Is it gone forever, or does someone know of a back door?
Unless you can find where it originally appeared, a lot of David's content is taken (with consent) from various forum posts around the web, that's certainly the way he gets all the ones by me that he has put on his site.
I don't think that is the same article. The one Duncan is looking for is one on making piston rings from carbon filled PTFE. I think it was by 'Journeyman'? and refers to the rings for the Boxhill that he was building.