They all look okay to me. The middle one is referred to as the "large rollmark" (take a wild guess why) and the other is the "small rollmark".
The LRM was the first marking and was used up until around 1978, when the SRM was introduced and used up until 1983. The new Series 70 replicas also use the small rollmark, but get this: Colt made up a batch of LRM slides just prior to the re-introduction of the Series 70 replicas that were large rollmark. They can be identified by the fact they say "Colt Competition" on the opposite side.