Thanks for your detailed reply, Pete.
Interesting. I have just checked measurements on another unmarked fretless board. From nut to centre of the two dots at the 12th is 17 inches bang on. To the centre of the two dots on my SB301 is the stated 16 12/16 (16 3/4) inches. It would explain why, before the rebuild started, with my standard fingering, above twelfth was not intonated properly. I had to compensate. The old bridge measured at a 34 inch scale.