As I just picked up the Gyromatics Arrow Dial from service, I now had the opportunity to take some side-by-side (top-on-top) photos with the other recently found silver sunburst Gyromatic.
Both share the same case with small differences. The Arrow Dial case has the spring bar holes punched through and the more rounded crown. Anything else is the same.
On the buckles, one is 12mm and the other 14mm. The 18/12 strap is a NOS GP lizard strap.
if my eyesight is not failing me, then the Arrow Dial has a 6250A between the lugs. The other has nothing, so not sure what the Ref is. Movement in both is 31.09.