Unlike many other European manufacturers that used acid-etched “pin-prick” codes, Tesla typically used a two-letter stamped code printed in ink. Because this ink is topical, it is much more prone to fading or rubbing off than an etching.

Where to Look

• The “Side Stamp”: Most Tesla tubes have the date code stamped on the side of the glass envelope, usually opposite of tube type.
• Ink Color: Early Tesla codes (1950s–60s) were often stamped in a yellow or white chalky ink. By the 1970s and 80s, you will more commonly see yellow or silver/grey ink.

Example:

This tube has HL date code. Based on the table below, it was made in 1972