Might have been one of those Monday morning Sales meeting where they decided they wanted a different rear sight on the CD's after production had started. Who knows?
Our job is to find what they did not the reason why.
I think the KISS principle would indicate that all barrels were cut for dovetails for 99's so they could produce barrels quickly. When they pulled a barrel for a 99CD, they tapped it for the Williams sight.
I haven't seen a picture of a 99CD without the rear sight that didn't have a dovetail. Some of the pictures you can't tell if they had screws.. but they all had dovetails.
