Good day...perhaps this can be of some assistance...
Yes the wind noise COULD be a dirty capsule but it can also be a failing tube (which wouldn't be unheard of in older mics)...the UM57 uses an EC92 triode which can be replaced with nominal relative skill. Yes microphone diaphragms can still function properly with that kind of "damage"....the gold is there to receive the polarization voltage creating an electrode out of the mylar or pvc diaphragm....(M7's can be made of mylar but are usually pvc and if yours is the original capsule then it is pvc)...so unless an enormous percentage of gold has been removed such that conductivity ceases you shouldn't experience too many if any deleterious effects.
However being that M7 capsule are glued to the backplate, depending upon the pressure used, coming into direct contact the membrane can also have unforeseen affects upon its tension...
...While my aforementioned statements hold themselves to be technically true in a purely statistical sense, it is far and beyond an unacceptable state for such a capsule to be in. Good news for you...Mr. Siegfried Thiersch, who is of former Gefell employ can easily reskin your capsule, lovingly, with authorized care...(he is currently, as far as I know, the only authorized Gefell capsule technician). His turn around times are fast, his service and worksmanship are top-notch, his rates fair (lower than 2k for a rediaphragming...actually lower than 2k for an entirely new capsule...more in the neighborhood of $4-500...however don't quote me on that & please contact him for accurate & current rates) and one of the only few in the world who still work with pvc. He is a world recognized authority (Mr.Heyne many times outsources to him, as does Tele-usa and many others)... Thiersch elektroakustik
...contact him and you should be pleasantly surprised.
capsule work should be treated very delicately, and really should be performed by technicians with the appropriate tools. The gold applied to the diaphragm is only a few angstroms thick in some cases and gold doesn't hold especially well to mylar in the first place (some use a nickel substrate first for better adhesion then gold on top), making it quite easy to remove.
I hope this was of some help, good luck.