Here is Keller's US patent for 45/45 disk cutting:
http://www.google.com/patents/US2114471

According to this web page:
http://www.stokowski.org/Harvey_Fletcher_and_Bell_Labs_Stereo.htm
(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:
>
> http://www.doramusic.com/patents/394325.htm
>
> Peace,
> Paul
>
>