Hi, some assistance, not an answer. It can't be a Don Louis ( wrong serial format and should be on BB), I've never seen a Hurlow with this fork crown, and I can't really see it being a Hurlow build but !!! The key to this may be the fork crown, it is not a standard choice so concentrate on this. I'll throw another Shop into the ring, I had a wally green built Mal Rees ( full wrapover stay ), the Mal Rees serial number is below and looks similar format. I hope some of this helps, Terry.
^ I’d say that’s a pretty good fit oldtel! Same dropout, same number format/position/style, same chainstay end. It can be really hard to ID a 50s frame when it’s got uncut Nervex lugs. Unless it’s got fancy cut lugs which give away the builder, or other specific mark that the builder used to put on his/her frames, it can be a tricky process.