Here's another little datum point.

As I already pointed out, the serial number on the Olympic Sprint (60224) is much higher than mine (1492). And we don't have a photo of that serial number.

On this forum I found a thread about a 1960's Holdsworth-made Claud Butler with a photo of the serial number 69537:

.

The location, at least, matches mine. Maybe even the font; though we have only the 9 to go on.