One thing you could do- try to flatten and square up the broken out area with an angle grinder, then weld a piece of leaf spring into it. Dump truck leafs or something similar are often up to 5" wide x 1/2" thick. If you can get a full stack of old ones from a heavy equipment company like I did, several will already be flat.
Bevel the edges of everything hard so you can get deep penetration with multi-pass welding. Pre-heat to 450 degrees or so before welding. This can be done with a rosebud torch, check temp with a tempilstick of the right temperature.
Use 7018 for welding the face plate to the old one on the top. Use 6013 or so for welding the plate to the wrought body. Such a repair may not make it rebound as well as it once did, but will at least give you a hardened face that will resist denting and marring.
This is what I remember from reading stuff on anvil repair. There is a very good article on this in an old issue of Hot Iron News, a publication of the Northwest Blacksmith's Association. Perhaps you can track it down. Or, at Ron Reil's blacksmithing page (currently hosted by ABANA) you can probably find more about it, as well as TONS of other great smithing knowledge, in the volumes of TheForge that he has compiled and available for free download as .zip files.
Anyway, great score for $13! It's great for a hardy tool holder, if nothing else.