I read these were popular during the Civil War as guns purchased by US soldiers as personal carry guns, because they were cheaper than Colts.
I'm sure a few were carried by Officers.
I don't think Double Action was as big a draw as we think today, back then, but it's a selling feature and Cooper wanted to make $$ like every other gunmaker.
I'd imagine the DA mechanics were delicate like early Colt DA's but collectors seem to feel Cooper made a nice gun, comparable to a Colt. They were probably popular like the Manhattan Arms guns as something to carry around town or keep under the bed. $15 was a lot for a Colt if you could get a "knockoff" for $7 that did the same job.
I'd be a little afraid of the DA being out of time and capping one off out of battery.
