Old Shure cart, a mystery to me….

[rito25]

And sure enough, the stylus LP Gear sells for the M91ED has that diamond shaped shank. I'd be concerned that forcing the wrong stylus into the cartridge may have damaged it internally.

John

http://www.lpgear.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=LG&Product_Code=SHSM0091EDS

Skip that stylus, cheap Mexico made.
If you want to test the cart out for cheap get a cheap Pfsatnihel off ebay. The sound good and have nice diamonds, plus save you from buying the expensive Jico. The M91 is a very nice cart, second from a V15 T III back in the day.

 

[Nat]

Back in the mid 70s, the M91ED could be bought all over the place for $14.95. I never bought a new stylus, just new cartridges. A good sounding cartridge but very affected by loading. Low record wear and easy mounting etc.
Certainly you might be able to stick a pickering stylus into an M 91ED, but the internal geometry of magnet and coils might not work ideally, and it might damage the internals of the Shure, or constrict movement of the magnet in the squashed in tube of the Pickering.
Various places MCM, Parts Express, Mat Electronics and others have generic replacement stylii for the M91ED for prices started at 9 or 10 bucks and going up. The low end ones have a bonded diamond rather than a nude diamond, and the cantilevers seem a bit imprecise, but probably sound decent. If you pay more, make sure you get more.