CBS if I recall correctly but it could have been RCA first issued 33 1/3 in about 1933 but it was wide groove and on shellac, it may have been wide groove on vinylite. RCA developed Vinylite as far as I know. So they all stole off each other. There was some lectures given by who ever the top bod at EMI was in or around 1950 and the ideal speed if I recall correctly was 55 rpm. It's in the early post war issues of BSRA (British Sound Recording Association) pamphlets I have the one issued after WWII the first meeting since 1939, along with a lot of the others right up to about 1955, found in 1936 and I believe the UK equivalent of AES merged into something or other in the late 1960's.
There were BS (British Standards) issued for tape speeds, track width, records all speeds which included details on lead in, lead out, banding, disc size etc. Again in BSRA along with standards for tape reels etc etc. Standardised globally circa 1954 with the introduction of RIAA (which is the RCA Orthophonic Curve used for 45 rpm discs.
EMI adopted 45 rpm and LP in or around June 1952, Decca having introduced 33 rpm in 1950. AR Sugden (Connoisseur) had a two speed turntable in 1950 and 3 speed in 1952, preceded by 78 rpm only in 1948. His cutting lathe did the same, his stereo cutting head was in development from 1952 and was shown at the Audio Fair at the Russell Hotel in May 1956 the same time as Peter Walker (Quad) showed the ESL 57. Vertical, Horizontal was Arthur Sugden's format for stereo disc, he had the UK majors at his door along with stereo tape machines to cut some masters. EMI discovered the Blumlein Patent as Bell Labs were trying to take all the claim, so through international agreement 45/45 stereo was decided upon as the international format and Sugden's method passed in to history and remains mostly forgotten, he is mentioned in Audio Amateur circa 1989. Which can be found here:
https://www.americanradiohistory.com/Audio_Amateur.htm
I suspect although his was the first stereo disc format demonstrated, that others were working on it as stereo tape had been around since 1952 in US (not commercially until the about the same time as UK. EMI and Decca were making stereo tapes from 1954 as masters. His concern was that stereo tape would oust the disc, so he set about developing a stereo cutter head.
I suspect the reason a standard was found for RIAA was due to the development work in Stereo disc recording, interchange of tapes, master discs and a global standard for all of them makes sense. IEC is better than NAB as a tape Equalisation so not all things American are better.