Pre-WWII Royal Tank Corps/Regiment Mess Dress Coat & Vest, Fine Condition

Description

Per the previous collectors tag, this is a pre-WW2 mess dress jacket and vest for a British major.  Silver colored Royal Tank Corps insignia on either side do not appear to have a makers mark on them (though I only peaked at the backs, didn't remove them to look). Majors rank on the shoulder looks a bit unique and different than others that I have seen, but appears original.
Inside of jacket has red leather along the lower edge, and a fine red quilted lining.  I do not see a tailors label inside, and it is not named.  There are a few stitches inside starting to come loose as is to be expected for the age.  Exterior of the jacket has minor moth tracking overall, with a handful of true holes in the dark blue of the coat, none greater in size than a matchhead. Majority of mothing is on the sleeves versus the body of the jacket.  Needless to say both jacket and vest are a small size by todays standards.  Perhaps a suit size 34 or 26.
Vest appears to have had buttons replaced, not sure if these are the original buttons just resewn or true replacements. Inside of the vest is stamped Chrisdie - not sure if this was the wearers name, or the manufacturer, or perhaps a costume house? Vest shows soiling and light staining overall. Adjustment buckle at the back is maker marked WHL & Co France.
And in looking closer, I just discovered a manufacturers tag in the vest with a New York location.  So not sure if the vest was added to the coat at some point, or if it was a piece tailored in the US?