Also- check between the pins for a diamond, molded into the glass envelope’s bottom. Some other companies manufactured tubes for Telefunken. Those with diamonds are worth more, if they test well, as mentioned above. Some of the smooth plate Teles are quite rare/desirable. You may have struck gold! https://www.tubedepot.com/products/telefunken-ecc83-12ax7-smooth-plate Lots of info here, regarding the variants from Tele: http://www.audiotubes.com/12ax7.htm
How much are these tubes worth?
I recently acquired an HP Standing Wave Indicator and they had 2 tubes, but the prices vary from $16 to $130 from the sites I looked at. They are 2 ECC83/12AX7 with labels saying "Made in Western Germany" and "TELEFUNKEN". Any idea of how much these are worth would be much appreciated.