This 1946 article by Philips provides background on the inception of the Rimlock (B8A) type valve. Philips acknowledged the existence of the American miniature (B7G) type, and explained why a larger envelope with more pins was required.
Philips Technical Review 194610 Rimlock.pdf
Philips’ view on the similarities between the Rimlock and noval (B9A) types comes out in this 1949 item on the EQ80 enneode.
The early history of the American B7G valve is provided in this 1947 RCA article, at the end of which is mentioned, in a matter-of-fact way, RCA’s apparent first noval release, the 12AU7.
RCA Review 194706 Minaiture Tubes in War and Peace.pdf
Cheers,