So, just found a beautiful copy of an Agfa Isolette III in a rather fine state with a Solinar f4.5 85mm. The seller claims the lens is in good shape but describes significant coating loss on the front element (no significant scratching though) and is appreciated in the photos. Should this be a concern?
That sounds like my old Solinar. It turned out to be unusable.
OP, if you can get the camera with the right of return, buy it, test it promptly and return it if it fails acceptance testing. If the seller won't agree to this, wait for a better one. They're not that rare and there are other functionally equivalent cameras.
I am not sure why the lens would be unusable unless it were damaged in some other way.
I currently shoot a 1935 Agfa Jsolette with the Solinar 85/4.5. It is an uncoated Solinar but still takes very good photos, even with color slide film. It does flare quite a bit if you point towards the sun so a lens hood is recommended but I am very happy with mine and use it constantly.