In 3rd gen. guns what is the difference between a 4566 for example and a 4566-1? Thanks.

Usually a engineering change, on the full size 4506 it's when they started using the heavier frame and slide of the 10mm. That frame doesn't have the "step" in it above the trigger guard towards the dust cover. I would guess it's the same on the 4566.

Near as I can tell from the Standard Catalog, the original had a first generation trigger guard and the (-1) denotes a 3rd generation trigger guard.

Ok, interesting. As I think about it I don't recall ever seeing a 4566-1 but rather just the -1 on the 4506. I believe my 4566 is of the latest frame design as you have alluded to (no frame step,rounded trigger etc.) but has no -1. Thanks for the
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