The fret markers are making me wonder if it's had the fret board replaced? My experience is that 3 dot markers were more the norm. I'm guessing circa 30's -- but that's just what I would guess left to my own thoughts. Catalogue guitar?

If you find a grungy old boot lace, you could mod' it to look like a "...Martin?/Ditson?..". You would need to break the neck, and roach it out considerably to command the big bucks tho.

Nice to see an old 'Mystery' preserved.