Marcel, that is a very nice holster and the "Pull The Dot" fastener appears to be GI-spec. However, I'm not sure the holster was modified from an issued type. It appears to be a private-purchase holster that was field-modified to individual taste. In any event it's a great addition to your collection.
Given the other pics that have been posted in this thread, I'll take yet another opportunity to boast of my 1943 Remington Rand M1911A1 and mint original holster . . . :twisted: