Looks like a Hot Heads cover with fins. Maybe they did a short run of finned... http://www.hothemiheads.com/desoto/cam_shafts_timing/timing_cover_52-57.html
TR nailed it. http://hemireveng.net/Desoto-Hemi-Firedome-C178838.aspx?sid=17972 Crap, I can see a few more hundred dollars to be spent on another project that is way back in the wings.
Thanks for helping me figure out how to spend another five hundred on a project that is probably three or four years out as far as getting started and worked on. I've had a 56 Desoto Hemi sitting out in the milk house for around 20 years waiting it's turn to be put in hot rod.
The same guy sells a really nice oil pump kit and people had a hard time getting a hold of the guy. It appears he is the only one selling that timing cover. I can't seem to find it anywhere else. Check the oil pump thread in the Hemi Tech section. I can't remember which thread it was, but they had a way to get a hold of him.
Peter Neuschwander is really hard to get hold of. I have found him at a couple of swap meets over the years and have some parts from him including a 6-71 blower adapter with pop off valve which fits an Offy 2-4 Dodge Red Ram intake. I think he lives in Castro Valley CA in the Bay Area but that's all the info I have....