I got one of those long ago as a gift, in the instructions it stated that the maximum MPH is would work with was 19!
I tried it anyway, and found out soon that it was too easy to find 20+mph going on any downgrade of any length.
Bye, Bye it went, too bad as this was pre any alternatives, later IKU came out with a wheel driven speedo, that many in the North Hollywood Wheelmen used, probably due to the use of a speedo by Ron Skarin.
John Jorgensen
Torrance Ca USA