I had read that in the Collier's Magazine of March 30, 1956, there was a Smirnoff add which featured George Jessel and his claim to have created the Bloody Mary. And that this was one of the earliest known references to it. So I've had an ebay alert set for this issue for a while now, and it just popped. Here is a camera picture of the add in question, which appears on page 65 of that issue.
NOTE: We were running out of database space, so I reduced the size of this image down. If you need the full-size scan, please let me know.