Earliest models may have no mention of any US-patent of metallic parts. You have to understand that bakelite is a very hard and abrasive to machine material, requiring tool to be re-sharpened very, very often.
There are patent numbers on both sides of the magnets but I would assume that these would not include the serial number.The former owner claims the guitar was manufactured in 1946 but there are no obvious numbers on the instrument to confirm this.The guitar is solid black bakelite that sunbursts to a grey color in the center.It has six strings and the headstock has Rickenbacher Electro written on it(both are written horizontally).Triangle fret markers, R tailpiece, set-in neck, 2 vintage single-coil pickups, stereo and mono output, and deluxe machine heads.
Re-create the jingle-jangle sounds that defined a musical generation with this semi-hollowbody featuring a very playable slim neck, and comfortable, all-around contoured body.
So, don't be blended by a shiny set of plated body cover plates.
Look at the body first; check the edges, the frets and the orientation of the plug, then the pick-up size and style and any patent information.
As on the "Fry-pan" they all featured an electromagnetic "Horse-shoe-magnet"-pick-up, invented not by Mr. "Bakelite"), black in color (much like the old telephones), a concept for which the company immediately filed and received a patent. This was the first electric solid body instrument with this feature ever (a feature they seem to have forgotten to file a patent for...
Oooops).1 or 2 controls: If two, they're located on opposite plates, not both on the treble side plate.
The company says to have no records of any of these. The neck was solid cast aluminum and the string spacing similar as on a B7., please keep in mind that the early Rickenbacher company was a young enterprise in a brand new industry.