Here is Keller's US patent for 45/45 disk cutting:
According to this web page:
(which accurately quotes some liner notes to the two Bell Labs LPs, which own; I cannot say for sure
other info is true),
The Stokowski stereo recordings were indeed two cutters somewhat similar to Emory Cook's method, but
of course for wide-groove.
Keller's patent was awarded in 1938. I don't think Keller's patent "lapsed" as stated on that web
page. I do think Westrex inherited the patent and this collected a lease and license fee on their
stereo cutters (the fees were not so onerous as that Westrex wasn't the first "industry standard"
stereo LP cutter).
-- Tom Fine
----- Original Message -----
From: "Paul Stamler" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, August 30, 2014 4:01 PM
Subject: [ARSCLIST] Blumlein's stereo patent...
> ...is here: