My understanding is Colt 'Blems' are supposed to be cosmetic only, not functional issues.
I looked at one here recently, and I couldn't find any blemish - just usual Colt rattles which are more like a Colt special feature.
After further discussion there was a mention of 'aged inventory / old stock', as Slapshot mentioned above..... I am sure there are occasional actual Blems, but it's very possible you won't find anything either.