Made in G.Britain by Mullard (1950s).
Smoke glass, Brown base, Bottom D-Getter. Can bring to you the superb sound.
Nearly same as 6SN7s family and can be replace for them BUT can be not used for replacing where the plate volate over 300V. 
Nos in original box.

Made in USA by RCA (1960s).
Muddy black plate, Triple mica and Double D-Getter with five supports.
Most of muddy black plate version are made by RCA.
Very warm sweet sound, great on voices and jazz. Long life tube (10.000 hours)
Nos in original box. Matched pair are available.

Made in USA by Sylvania (1960s).
Black plate, Silver top with O-getter.
Very good tube.
Used but tested as new. Packed in white box.
Matched pair are available.