This is a vintage (old stock) Telefunken 6BQ5 tube.  I have had this squirreled away in my private stash for more decades than I can remember.  Tested as follows

Emission on a Jackson 648S = 105% with 70% as minimum.

Gm on a Hickok 534 (same as 533) = 8,500 with new tube to test at 7,500.

IOW, tests as a new tube.

Telefunken 6BQ5 tubes are in a league of their own performing far above other brands.  Hate to part with it, but I don't have any amps or receivers that use 6BQ5 tubes.  I build new amps but use Type 45, KT88 and maybe 300B output tubes.