The Hammerless Double was available shortly after the Civil War, in the 1870s - but for most folks - it was too expensive.
Initially, they were found on the better grade of shotgun - more of the province of the wealthy sportsman than the working man, and so, folks of the time spent their money on the ruggedness and practicality of Hammered Doubles.
Westley Richards - 1870's
Baker - 1881
Remington - 1882
Parker - 1882
Colt - 1883
Harrington and Richardson - 1883
Lefever - 1885
Sawed-Off shotguns generally featured hammers, since they were robust and rugged, they allowed a second try at detonating a recalcitrant primer - and were cheaper to purchase, besides.
Vaya,
Scouts Out!