Tony, I would question that he is wearing medal ribbons. Certainly the white blob on the pocket flap is not the ribbons, since ribbons were worn above the pocket seam. And the fuzzy bit above the pocket which I assume you are referring to would be an awful lot of medals to occupy three rows. Also both 'blobs' have a fairly marked shadow under them suggesting that they are not flat but three dimensional (see image below).
That said I can't offer a better explanation for what these features are. It may be significant that although the photograph is relatively free from marks, the only apparent defect is the black dot on the same man's tunic pocket. And if these are the medals ribbons of a deceased relative, why aren't any of the other men wearing any ribbons at all? To be in the MPSC they must have volunteered to transfer after 1903 when the Corps was founded. The MPSC was only staffed by existing servicemen, and did not (and still does not) directly recruit civilians.
