I dig the pickguard!
Cool little parlor. Looks like 1920's or 30's. It was made for steel strings but I would use extra lights. I usually put d'addario custom lights on little parlors like this. They are a little lighter guage than d'addario light's and to my ears sound really good on these old parlors.
I sincerely hope you don't need to refret it. Those old dyed wood fingerboards are often extremely brittle and just want to fall apart when you pull the frets.
Definitely pre 1926 due to the tuners reverse gearing. I use D'Addario extra lights myself. Great little guitar.
Can you take a picture of the bracing? Fan, x-brace or other?
Pickguard, dyed fingerboard and painted bridge look like later instruments, near the Tonk days, so I'd say late 20s.
I like everything about this ol'treasure except their funky logo ! Headstock/neck maple...oak? Brace grain wild...silk & steel would probably work better than full metal.
Too bad you can't replicate the decal as an inlay by someone like Larry Robinson without devaluing it. I'm up in the air about some modifications, but this Regal is old enough and rare enough to be a historical item and therefore out-of-bounds.
I have an 1898 Lyon & Healy parlour guitar that has wonderful folk art fretboard inlays. The tailpiece was engraved with a signature in 1901, probably by the inlay artist. I wonder...would a replica inlay of the label be a plus in another 100 years?
Spent some time trawling the net looking for information, found nothing to add to what has been said already. However Amazon have this book http://www.amazon.com/Regal-Musical-Instruments-Bob-Carlin/dp/15742... your local library may be able to help you sourcing a copy.