I have no 'dog in the fight' so it matters not to me - but - logically If the Coast Guard Auxilliary Service were going to mark their rifles would it not be more logical to mark them
CGAS, or CGA, or just CG
CAS could just as easily be "Central Authentication Services" or the "Cinema Audio Society" (and yes - both of these exist)
I wonder if sometimes we just attribute something we 'would like the marks to mean' rather than saying 'we just dont know' ?