When I had my '65 Mustang (WORST POS I ever owned) the speedometer failed so I ordered a new one from one of the most well known suppliers of Mustang parts.
The speedo arrived and the box had a fancy, iridescent, label on it proudly proclaiming it to be authorized by FMC.
After installing it (another pos I might add) I backed the car out of the shed and upon moving forward the speedometer jumped to something over 40 MPH (I forget exactly how stupid it was) and stayed there.
I called the company where a fairly crabby lady answered and reluctantly sent me another one.
THIS time, when I got on the road, it hunted all over the place........ 🤬
I called RA and asked the person who answered what their experience rate was with the speedmeter THEY sell to which he replied 100% satisfied so I ordered it and went through the whole stinking process A G A I N.
The only difference this time is it worked!
Needless to say the previous vendor was not happy.
Well DUH.......neither was I!