The "font" for the numbers stamped in the cylinder give mixed signals. The 3 looks identical to the ones Colt used in all other places, but the 4 is a little different in that the tops of the 4s don't completely meet on the cylinder while they do on the frame.
Dfariswheel's comment about counterfeit "Poopers" has gotten me in a suspicious mood. I can't detect any evidence of welding, but I can possibly detect a faint color difference between the finish of the frame and the finish of the barrel and sideplate. If the frame was from a Three Fifty Seven originally, the serial would make it a 1954 one, which would indeed have had the Dual-Tone finish and therefore explain the presence of the satin flutes.
There's as many things leaving me with doubts, however. I find it very questionable that they would do such an extremely fine job reshaping the frame, polishing all the other satin surfaces off, and even changing the medallions in the stocks to gold ones, but then entirely neglect to also correct the cylinder flutes. Especially considering that the numbers stamped into the cylinder also have bluing over them, meaning the Colt factory either put them there originally, which does not appear to be the case, or they were refinished over -- by someone who either put the bead blasting in the flutes or managed to leave it there somehow, neither of which makes much sense. The barrel is also the early hollow underlug type used from '55 to '60. If it was added in the late 60s, would they not have more likely used the later style barrel?
Very strange. Curiouser and curiouser.