It was customary in the 50's for manufacturers to deliberately make speedos read fast but with reasonably accurate odometer. With my '56 KHK it reads very fast. So I started thinking...
The speedo is driven via 1st gear splined to the mainshaft to 1st gear on countershaft. In 52 this was 18 to 29 teeth, in 53 18 to 27 teeth, then 54-up 17 to 27 teeth.
Then the speedo spiral gear fitted to 1st gear on countershaft was 7 starts in 52/53 then 54-up 8 starts.
Then the sprockets were 21/51 in 52/53, then 54 up as different as 22/49 (though other possibles).
Then nominal tyre circumference was 6.68' in 52/53, and down to 6.55' 54-up.
Do the maths and presuming they started with an intentional 10% fast speedo in 52, because the speedo didn't change, by 56 it could be another 7% fast.
The K speedo does look cute though!
I must get out more...