Hello, I think the plates are a little thicker so it doesn't red plate (glow in the wrong areas) as easily as a regular 6BQ5,
and maybe its redesigned with slightly bigger spacing. The vent holes are different, and it has 2 getters instead of just one.
The military (EL84M) ones are designed for 10,000 instead of 3,000 hours. But that's when used conservatively.
USA 6BQ5s were rated for 300 volts max, but Dynaco Voxx Scott and guitar amps often run them around 420 volts.
I know 2 people that have VOXX 6BQ5 amps, and they only get about 50 hours out of new 6BQ5s, because regular 6BQ5s run so close to glowing.
I've restored hundreds of vintage amps, and even with new coupling caps, vintage 6BQ5s run very close to glowing dull red (which wears them out very quickly). If your amp is 14 watts/pair of 6BQ5/EL84, you probably can get by with regular 6BQ5s. If your amp is rated for 20 watts/pair, I'd use these.
The extra getters make them last longer. Thanks, Joe