Board Thread:Questions and Answers/@comment-1904000-20130601230733/@comment-1504072-20130602025057

There's no official word, canon-wise, on what significance the coat has to FOX/FOXHOUND. It could be official dress for both units, FOXHOUND having adopted it from FOX, or it might simply be a personal copying of styles (Gene > Big Boss > Liquid's unit). From a story perspective, it looks like it's meant to highlight the similarities between the characters who wear it. From a design perspective, I suspect it was to hide the awkward shoulder joints for the PS1 character models, especially Liquid, similar to the shoulder pads on Solid Snake's Sneaking Suit.

Big Boss seems to be the only one to wear it during his time in command of FOXHOUND, but then we don't have much info to go on. Under Liquid Snake's command, Ocelot, Mantis, and himself all wear it at some point in MGS1 (the other three members wear it in various artwork by Yoji Shinkawa). Interestingly, Roy Campbell is shown wearing it in Shinkawa's artwork for the non-canon audio drama.

There may be some word on the coat in the FOXHOUND equipment article, but I doubt it's much more than a sentence or two, given the lack of info.