Someone correct me if I am wrong, but I think the only Colts that had acid etched barrels were the "Colt Frontier Six Shooter" model 1873 and 1878 DA; the .38, .41, and maybe .32 caliber 1877 DAs; and the 1878 .45 Colt caliber DA that had "Omnipotent" acid etched on the barrel. The Omnipotent marked 1878s I think were only sold by Benjamin Kittredge of Cincinnati, Ohio. It is also my understanding that he coined the other etchings as well. And, I read that he came up with the nicknames for the different caliber 1877 DAs. "Lightning" for the .38, "Thunderer" for the .41, and "Rainmaker" for the .32 caliber. He used all of these names for marketing Colts revolvers. I think towards the end of the 1880s, it became evident that the etching was somewhat fragile, and they went to a rolled on stamp marking.