Daytona or 275 speedometer calibration

Hi, Many of the Speedo calibration shop websites give useful formulas for calibrating speedos ( if you change axle ratio/ wheel size/ gearbox swap etc). The default number they all seem to give for the ‘number of cable turns per mile’ for speedos running in MPH seems to be 1000.

That said, my MPH Veglia Borletti speedo (from 1967) is stamped on the rear ‘1610REVs=1M’, which I’m obviously assuming means it actually runs at 1610 cable turns per mile and not 1000.

Does that sound correct?

I’m thinking maybe the 1000 figure became an industry standard at some time after this gauge was manufactured.

Thanks in advance for thoughts.
J