You are looking at a Colt Commander that has been converted to Double Action by the Gunsmith Seecamp. The DA conversion required a lot of machining, and the old serial number was cut away. Each pistol then required a marking variance from the ATF for permission to re-mark the serial number at a new location.
From a distance you might mistake this for the Behlert pivoting trigger from a distance but this is a Seecamp DA conversion.
Why do this? I have no idea. To have something different at the time I guess.