155-0026-00
The Tektronix 155-0026-00 is a custom chip for the 7000 series readout system, packaged in a 16-pin plastic DIP.
It is an analog read-only memory used as a Character Generator for code row 5, 10 letters (S V A W H d B c Ω E).
The letter "S" is in upper case, therefore the 7000 series somewhat incorrectly display time units (e.g. "mS" which would actually indicate milli-Siemens instead of milliseconds).
The chip was designed by Barrie Gilbert.