did someone say math.....
Not sure if it's a 1 speed or 2 speed, but here goes
On a puch e50 with 18 x 36 gearing with standard 17" tires would need around 10,800 rpms. Seems plausible to me. My ped would need about 5 miles to get up to that speed with that gearing, but it's possible.
Elliot, call someone and take a picture with your cell phone of both the tiny tach and the gps at 70 mph. Much safer :)