This rare 5-string Broadcaster was made in England c.1935. The resonator is mounted with five wood screws and easily removed. I have played it open-back since buying from Jake Wildwood, a professional repair and restoration guy, in 2012. It is very sweet and solid. With a mahogany neck, oak rim, hoop metal tone ring, and skin head, the tone is strong and balanced.
Wildwood describes the work he did (dowel re-glue, fret level and dress, etc.) and gives extensive descriptive comments in his 2012 post: jakewildwood.blogspot.com/2012...olin.html . See that for many more details and photos.
The resonator does what they're supposed to do. Relative to open back, the highest overtones are stronger. This is heard in the timber and in the sharpness of the attack. The projection is more directional. But obviously, it's not a Mastertone sound.
The basic specs: 4 lb 9 oz as open-back; 5 lb 12 oz with resonator. 25 1/2" scale; 10 1/2" head; 1 1/4" width at nut. 22 frets; with the current 5/8" bridge, 0.050" to 0.060" action at the 12th fret.
The visually remarkable yellow stuff is known variously as nacrolaque, pearloid, or MOTS.
The included hard-shell case is almost certainly original. Does the job but wouldn't mind cosmetic attention.
The manufacturer was J. & A. Margolin of London, and it was first retailed in India. (That company store still has a store in New Delhi.)