Recently I purchased a Pre-War Colt NM at an estate auction. It appears to be in original configuration and the individual had owned it since the late 40's. However, this NM has a flat checkered mainspring housing with a lanyard loop instead of a curved one. The serial# of C1999XX would indicate that it is a 1911A1 and should have the curved housing. Could this be a factory configuration or has the housing been changed? Any help from someone more knowledgeable than I would be greatly appreciated.