Some people call it an "idiot mark", but to many collectors it is simply called the "GI scratch". If you only have a small mark below the slide stop on the frame consider yourself lucky. The worst manifestation of this is when the slide stop slipped upwards and put a nice circular mark all the way across the slide itself.
The other common "blemish" is to find all sorts of marks and scratches on the frame under the slide stop from trying to pry the latter out with a screwdriver. On the other side of the pistol you may find evidence that somebody was banging on the slide stop pin with a drift punch and/or hammer. All these are the result of somebody having no clue how to take a 1911 apart. Sometimes it happened while in the service, sometimes it was caused by a later, ignorant civilian owner.