Wow!! Good buy!! That is the quite scarce Two-Bolt Model. This one has been on GI for some time --
http://www.gunsinternational.com/Ith...n_id=100242606
The entry-level Ithaca hammer doubles were the X with steel barrels, the A with Twist barrels and the AA with Damascus barrels, all essentially the same except for barrel material. The B, C, D, and E all had increasingly finer Damascus barrels, increasing amounts of engraving and finer wood and checkering.
My A-Grade NIG is all original. I suspect the original owner got slapped in the face pretty hard with its 3 1/2 inch drop, and left it in the closet after that!!