Could be that someone has got it wrong in the description however............
A bit over a year ago there was a double for sale in the USA which was advertised as something like "500 Jefferies Rimmed (or flanged)".
Note the spelling "Jefferies" which was theirs not mine.
There was a thread on this forum at the time asking about the description and another member said it could be a 500 flanged Schuler.
Cannot remember the thread title or the dealer but it could have been cabelas or griffen & howe.
I think Hatari Times had done an article on that particular cartridge which is very rare but does exist.