Gen 3 slides are not compatible on Gen 4 receivers.So, Aim had some LEO trade in gen 4 19’s. The photo they posted shows a Gen 4 frame, but a non-Gen 4 marked slide. My first thought is that it’s a 4 frame with a mismatched 3 slide, but the serial number fits in the 4 range. So, question is, did the earlier Gen 4’s lack the Gen 4 mark Or is that a Gen 3 slide?
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