Sylvania was the developer of the Loktal tubes, which were a rebuttal to RCA's metal tubes. They were introduced around 1939, and quickly became adopted by Colonial, Philco and Zenith; the three manufacturers who were unwilling to use the metal tubes, and pay royalties to RCA for using them. All three had close ties to Sylvania as an OEM tube supplier.

RCA wasted no time in firing back with the all-glass miniature tubes, just as WWII was about to start. The Loktal tubes hung around for a few years after the war, but were pretty much obsolete by the early 1950s.

There is one major advantage to the loctal today compared to the octal for audio applications: price!

I don't claim to be able to hear the difference between different tubes of the same type, ie tube rolling, as I'm slowly going deaf in one ear. That said, I do know that my wallet much prefers spending $3 on a 7N7 vs $10 on a 6SN7. In particular, some Sylvania 6SN7s can fetch $100+ for a single NOS example on eBay, whereas literally the same exact tube, with the same exact internal construction, but on a loctal base will net $2 to $5...

I won't use any of the extremely expensive octals in a DIY setting anymore; only the loctal equivalent if it exists. Paying more when you don't have to for equivalent performance is downright insane.