1892 Ih Reverse Die Clash Error

Looks like it matches up with the head dress feathers on the reverse. Die clash that was partially polished off?

Not sure about the feathers. It is too triangular and the feathers would be going into the wreath (unless I misunderstood you). Thanks for the input though. Any other ideas? Its a fairly nice coin with a small corrosion mark on the nose. I think I might send this one in for conservation and grading.

Die clash marks are somehwat common, especially on certain dates. That's a pretty detailed one. Most commonly I've seen them on the obverse - in front of the portrait by the nose (that half circle) and by the headress feathers (looks like fire between them).

A die clash occurs when the obverse and reverse dies strike with no coin in between to get minted. The Dies touch and impart some of the design from one to the other. Any coins that are made from those dies afterward will be affected.
So to answer your questions- I don't think that anyone has these listed as a variety. I would think that they qualify for being an error. Die clashes in general are not all that rare. I couldn't say if this one is rare, or worth a large premium.
You can search ebay for sales of similar coins and determine if yours is "rare". Here is one that is nicer condition and sold for $24
http://www.ebay.com/itm/1888-Indian...047675.l2557