As promised, here are the Tube ID Tips from the fine folks at TubeMonger:
"If you have handled enough tubes over time, you should be able to id a tube manufacturer and even vintage by just looking at the picture. Glass bottle, curvature on the top, internal construction, pins and glass interface give a lot of cues.
If you don't physical access to a lot of tubes, spend time online examining pictures. For example, search for Amperex or Siemens or Telefunken and see various tube types made by a single maker. You will start to recognize the bottle and internal construction. Over time, you should be able to id mis-identified, mislabeled and even recently printed fakes. Good places to start:
- various tube sellers that have pictures
- Saucer shaped getter - Russian
- Amperex/Philips tubes with different labels are identical if the revision and date codes are similar. Green, Orange, Globe or Bugle Boy labels don't mean much.
- Western European made E88CC/6922/CV2492/2493/E88CC-01 and E188CC/7308/CV4108/CV4110 always have gold plated pins - exception CV4109 flying leads.
- SQ or PQ - these are select special quality tubes culled from the regular production.
- Valvo rote-red or blue/yellow etc (hamburg made or sourced from Philips/Holland) - http://www.audioasylum.com/cgi/t.mpl?f=tubes&m=133875
- Tubes with Military markings e.g. UN-CEP, CV2492, CV2493, CV4108, CV4110, E88CC_01, CV4109 etc - have passed specific military qualification for that tube type. For example - http://www.tubemongerlib.com/gallery2/v/6922/Amperex+Philips+6922+1964-65+Halo+Getter+USN-CEP+Label+-+USA.jpg.html
- Instrumentation grade tubes made for Beckman, HP or Tektronix etc. e.g. http://www.tubemongerlib.com/gallery2/v/6DJ8/Mullard+ECC88+6DJ8+1976+A-Frame+Dimple+Disc+Getter+Orange+Globe+Amperex+Label+Tektronix+Select+-+Blackburn+Gt_+Britain.jpg.html
- Late 1950s onwards - Philips/Mullard and tubes from associated Philips factories worldwide always have etched date codes on side of the glass. Codes may be faint or hard to see. Good light and magnifying glass helps. Notive VR5 *4x in the following picture. :http://www.tubemongerlib.com/gallery2/v/7308/Amperex+Philips+7308+1964+Halo+Getter+HP+Label+VR5+Star4I+-+USA+.jpg.html. VR stands for tube type E188CC/7308 and 5 stands for 5th revision. * is for Amperex Armonk USA plant.
- early to mid 1950s Philips/Mullard and tubes from associated Philips factories worldwide may have date codes etched at the bottom between pins. Example: http://www.tubemongerlib.com/gallery2/v/6922/Amperex+Philips+E88CC+6922+-+1956+Pinched+Waist+Square+Getter+Heerlen+Holland+Prod+Mullard+Old+Shield+Label.jpg.html
- dimple disk getter - Philips/Mullard and tubes from associated Philips factories worldwide except USA
- 1950s-1960s Siemens Munich Plant tubes have date codes etched in glass. From 1970s codes were embossed on a metal chad attached to the getter posts or plate supports.
- Tungsram Hungarian tubes have metal tag with 2 digit embossed code attached to getter posts or plate supports.
- For West German tubes in particular - Falcon or Eagle logo means tube have passed Bundeswehr military qualification e.g. http://www.tubemongerlib.com/gallery2/v/EF86/Telefunken+PCC88+1968+Bundeswehr+Falcon+Logo+Diamond+Bottom+-+Western+Germany.jpg.html. Watch out for fake falcon/eagle logo on recently printed tubes of E. European origin (exception - Tungsram tubes with Siemens logo with falcon/eagle are OK).
Shall add more to the above list in future.
For your tube ID Questions
Hope this helps...