It was common through the 20's and 30's trailing into the 40's.
Colt manufactured many different types of plugs, switches and circuit breakers and boxes.
I have included a link below that will show some patents, but watch for dates as some of them patented even into the mid 30's were applied for in the 20's and approved later. These items would still be out on the open market as patent applied for, just not approved yet.
There are other items that they also made like bottle caps and commercial dish washers, but mostly Guns and Electrical items. Out of the Electrical it is mostly cut-outs.
Here is another link that shows mostly all of the electrical:
I hope this helps