Fantastic! What a treat. Given the clues, your bike must be a 1949. I have done a little more research and, even though there is no concrete proof, the model number would be best called out as DB-12 as I have documentary evidence of the Model DB-13 on a dated partial price list Effective June 1, 1949. There is no good explanation for what appears to be scuff marks where a tank might have been, but that is one of those historic realities we can't control. Speculating on that is pointless.
On close examination of the 1950 Schwinn Dealer Catalog art work, the straight bar on the 1950 D-13 and the 1950 D-12 is attached to the seat tubes and down tubes respectively in the same way as is seen in my photographic example, a 1951 Hornet with serial number stamped on the BB.
I'm glad you found the bike. It is unique, almost totally original and definitely a keeper, unless of course you think you should sell it to me

.
All the best,
Kit
Oh, one last thought; the serial number on your bike was stamped just 4 days before the death of our champion, Ignaz Schwinn.