BACH MOUNT VERNON C TRUMPET WITH CASE NR USED - eBay (item 380073556678 end time Oct-23-08 21:14:03 PDT)
This listing is on ebay, and it doesn't look like a C to me. I've seen many Mt. Vernon C's, and none of them looked like this. However, it does look like an Eb or D, based on the proportion of the bell to valve body etc.
Either this is a completely different and unique horn, or I'm just mistaken
Though you might find it interesting.