The 5 on the left toe tells us the gun shipped as a 45 cal originally. The cyl is a rechambered 357 or 44 Mag.
I tried the W and the U back in the .......70s?.....80s? I did not like them. Can't remember exactly why- something about the feel did not suit me. Bill Orr had a big box of each on his table at gun shows back then, so it's a safe bet many have been added to guns that did not ship with them.
The cylinder is too short to be a .44 magnum, unless the front has been milled back.