[NJARC] What's a Masterphone?

[amagoun]

Gary Saretzky, Monmouth County archivist, came across this device in an ad for in the December 7,
1921, issue of the Red Bank Register:

Santa Talks to Children.

Bring the children to Foxwell's, Monmouth street, and let them hear
Old Santa himself talk direct to them through the Masterphone. It will
delight them and will also be very interesting to you. There's absolutely
no obligation on your part in calling at Foxwell's and asking to
hear Santa speak.—

That's just slightly cleaned up from the highlight/copy/paste functions: amazing what you can do
with PDF technology, in't?  For the rest of the 28 pages in high resolution, visit
www.mtpl.org/data/rbr/1920-1929/1921/1921.12.07.pdf.

Does anyone know whether a Masterphone is a telephone, talking machine, or even a radiotelephone?
Gary couldn't get a clear answer searching the internet.

thanks,

Alex