I am wearing this today but dragged out this older photo because another thread has mentioned circular slide-rules and their markings.
The bits of rally route drawn on the map are from the Hereford Evening News Rally of May 1973. The car (not mine, I was navigating) had some "issues" and my diary comment was "Not a satisfying night."
One of those purchases that’s makes you wonder what you were thinking when you bought it. I’m pretty sure it was 50 bucks though I remember it costing much less than the service