I came across this on eBay (but, of course), and wondered if anyone 1) had seen anything like it before, and 2) would explain the raison d' tre of it:
T A old style triple crank right arm Item # 2172317848
http://ebay.com/
If you look closely at the two pictures, you'll see that there is an outer chainguard (which is not all that unusual). But look a little closer, and there's another(!) "chainguard" on the middle ring.
This setup seems quite odd to me, at least ...but I figure one of the CR list experts can/will enlighten me.
In correspondence with the seller, he didn't know what it was for either; he'd acquired the crankarm & rings as shown, as part of a lot.
--- brandon davis ---
-- sacramento, ca --