There is speculation that there are other speedometers that were used by Ford for the GP.  Some were made by Waltham and some are said to have been marked with shift points for the various optimum gear pattern.   This is purely assumption and not proven as yet by any documents with Ford monikers.
MB/GPW Gauges
King Seeley - Late (rear)
King Seeley - Early (rear)
Moto Meter - Late 
Moto Meter - 17963
Moto Meter- J.Rogers photo
Moto Meter - Slatgrill clone by Sean   
Waltham - Counterbalanced
Waltham - Counterbalanced (rear)
Waltham  (rear)
   Waltham-Al Brass photo
King Seeley - 4036BN
Autolite Slatgrill 
GPW-Long Needle-10/42
How to identify a WWII Jeep Speedometer by manufacturer (excerpt from TM 9-1829A) Manual 17mb download
download courtesy
Speedometer Photos
MB-GPW Speedometers
(click for enlarged views)
(click for enlarged views)