HELP....Zetor 3545 tachometer

[stuzetor]

I have a NOS (New Old Stock) tachometer still in the box with the part number 937001.My parts catalogue states the correct one for my Zetor 3545 model is 932003.What is the actual difference inside the tachometers as they look the same to me ???.
I have actually stripped down my non functioning tachometer as it would not turn and found the small bevel gear which works the hour meter part has "stripped" its teeth.Has anyone got an old tachometer for sale so i can repair mine ??.Thankyou.

 

[stuzetor]

A friend gave me a very rusty and damaged tachometer from his scrap Zetor 4718.I have very successfully repaired my tacho using some of the brass and plastic cogs / gears i removed from it .All i can say it was very fiddly but very rewarding