Edit: I initially posted this thread asking for assistance with measurements of several smaller Omega Speedmaster watches. I have updated the original request with measurements so far, but still ask for help from the OF community to fill in the remaining gap in bold below. Hopefully this will also benefit others looking for options of smaller Speedmaster watches and please add other watches at 40mm and under from the past not represented in this post.

1) SPEEDMASTER 38 CO-AXIAL CHRONOGRAPH ( 324.30.38.50.01.001)
Case: 38mm
Thickness: 14.7mm
6 to 12 lug to lug length: 44mm

2) SPEEDMASTER MOONWATCH CHRONOGRAPH 39.7 MM (CK2998 or FOIS; 311.32.40.30.01.001)
Case: 39.7mm
Thickness: 14.0mm
6 to 12 lug to lug length: 47mm

3) SPEEDMASTER '57 CHRONOGRAPH 38.6 MM (The 1957 Trilogy; 311.10.39.30.01.001)
Case: 38.6mm
Thickness: 13.69mm
6 to 12 lug to lug length: ?????

4) SPEEDMASTER DATE 39MM AUTOMATIC (3513.50)
Case: 39mm
Thickness: 14mm
6 to 12 lug to lug length: 44mm

 

Bump...
Updated with new measurement information in original post.

 

I measured 47.1 or maybe 47.2mm lug to lug on my 60th Anniversary '57 Speedmaster and posted it here before and received no response so I deleted it.

 

Sorry I missed it and thanks for reposting!

 

This is very useful. I don’t own an Omega Reduced but based on this Worn and Wound article,

SPEEDMASTER 38 CO-AXIAL CHRONOGRAPH (3510.50)
Case: 38.5mm
Thickness: 12mm
6 to 12 lug to lug length: 45mm