I have had a chronometric speedo for my Goldie, overhauled by Poples, and he does a first class job at a resonable price.
I had the wrong speedo head on the bike when i bought it.
It was reading double the speed and the face and needle was starting at 7 o'clock instead of matching the rev counter head at 1 o'clock
He fitted the correct new face and needle, and recalibrated the speedo gearing.
Now working perfectly.