The year of manufacture is encoded into the serial number engraved on the base plate of every Standard or Duplex Questar drive. The initial first digit is the last digit of the year of manufacture ("5" = 1965, 75, 85, etc). To determine the decade use this guide based on an inventory spreadsheet found at the Yahoo Questar group (which is difficult to join and navigate).
1950s: 2??-6?? The earliest models did not have the year code digit.
Numbers are approximate at the ends of the decades, but it will be obvious where yours falls. For example, if yours is 9-CV-4111-BB, then the 4111 means you're either near the end of the 60s or beginning of the 70s, so logically the 9 must mean 1969.
50th Anniversary models produced since 2000 do not have the year code.
Field Models do not have the year code. Known examples:
*According to very out-of-date Questar website.
For more info on what serial number codes mean and details on other models, visit the Questar Corporation web page here.
Edited by Optics Patent, 02 March 2017 - 10:33 AM.