Stronglight 122 BCD chainring variants
 

I recently dug out four different 122 BCD Stronglight chainrings for someone who needed one, and found that they varied in several ways. Two of them had "pointy" teeth. (One was actually unused and the other had minimal use, so the sort of "shark tooth" effect you sometimes find on very worn rings wasn't responsible.)

The other two had blunter teeth, similar to what you see on pretty much all modern chainrings.

Sorry, no pictures--they're in my phone, but resist transfer to my computer.

Also, one of the "pointy" rings and one of the non-pointy rings were drilled and tapped for a little screw and a spacer, obviously intended to keep the chain from wedging between the crankarm and the ring.

I've seen these variants before, but never really thought about them. I have a vague notion that the pointed-tooth design is older than the non-pointy one, but have no idea if that's really the case, or when the change from one to the other occurred. I imagine that the same may be true of the anti-chain-jamming screw, but again, no idea. I don't know the provenance of any of these rings, so it's also possible that different 122 BCD cranksets (93, 49d, 63, etc.) were outfitted with slightly different rings, though that doesn't seem especially likely to me.

Since I'm always eager to add to my little stockpile of arcane and useless knowledge, I can only hope that someone here will shed some light on this.

Hilary Stone's website has some images that appear to illustrate what you describe, though there is no explanation of the different tooth shapes, so hopefully someone can shed some light: Hilary Stone Chainrings 122mm BCD

Stronglight Chainring Tooth Profiles
 

Old style with pointed teeth. They used this tooth design on Stronglight 49 and 93 chainrings until at least the mid 70's. I liked these because the sharp teeth picked up the extended pins on old style chains better that say Campy chainrings giving faster shifts.

https://cimg5.ibsrv.net/gimg/bikefor...8ad177c1c0.jpg

The newer style teeth from late 70's.

https://cimg1.ibsrv.net/gimg/bikefor...331ae9b6b2.jpg

Stronglight used the chain catcher pins on the largest chainrings 50T ??? on up on their Ref 93, 99, 104, 105, 106 and 107 cranks. The part was # 64 on the earlier models and 63 on the 106 & 107 cranks. Never saw the catcher pins on Ref 49 or any of the later economy models.
https://cimg8.ibsrv.net/gimg/bikefor...68e56d9611.jpg
verktyg :50:

Yes, the third ring from the top on the Hillary Stone site--numbered ST122-3B--has the pointed teeth. It also has the little tapped hole for the anti-chain-jamming screw and spacer, although both screw and spacer are missing.

See? That was easy! Thanks, Chas!

"Mid-70s" is close enough for me. I had thought it might have been earlier, since I have a vague memory that my new 71 TdF came with the blunter teeth.

Stronglight also offered lower-level cranksets that used 122mm rings, I've salvaged rings from basic models of Peugeot as late as 1980's models.