Does anyone know who made this?
This is the only marking on it.  These are what were in my F2B when I got it.  I bought some Chinese Groove Tubes to replace them, but these sound noticeably better.  Much tubier.

 
 
Thanks,
 
Charles

Looks to me like late 80's/early 90's Chinese, which do indeed sound better than current Chinese, IMO.

Thanks, Kent!