I'm doing my daily due diligence but seem to have hit a brick wall here. As I read through all the watch sale posts I see very few with the Co-Axial movement. Is this because it's only used on relatively newer watches? Is it not considered that important? Is it even used at all on Speedmaster Professionals?

Many thanks for your kind indulgence.

 

Coaxial escapement is relatively new for Omega. First used in Deville by 1999, not until mid of 2000 that Omega used in broader model of Seamaster, Constellation and then some of Speedmaster line. At that time the coaxial was used as modification of ETA based model.
By 2007 Omega launched its 'all in-house' model caliber 8500 firstly used in Deville Hour Vision. It is a new caliber built ground up using coaxial escapement in the design. Later a chronograph version came out as caliber 9300.

If you refer Speedmaster Professional as the 'moon watch' and its derivative (LE, NE etc) then no they are not using coaxial escapement. It is based on Lemania 1861/861 manual wind which derived from original caliber 321.
However several Speedmaster professional series have coaxial escapement such as broad arrow 1957 (Cal 3313) or newer Speedmaster Pro with Caliber 9300.

Since many of our FS watches are vintage or pre owned early modern (pre 2005) then logically many do not use coaxial escapement.

 

omega's first co-axial, cal2500 had a series of problems, and came out in 4 variants a, b, c and d. The first 2 had a series of problems and aren't popular with collectors here.