Here's my IR electric that came to me from my father after he passed away in 1987. I have no idea how old it is, but I'm fairly certain I recall him using it in the mid 50's. He had been an auto mechanic from the 1930's, but had become a service manager in the 50's, so he had a lot of his old tools at home.
Anyway, it's labeled "Ingersoll-Rand, New York, London Universal Impact Tool, Size 8U, Model A". Marked 5 amps. It's a 5/8" drive, with a 1/2" adapter. I guess they once made 5/8" drive sockets?
I use it occasionally in my amateur car maintenance tasks; lug nuts, suspension work, etc. It weighs quite a bit, so one-handing it in awkward locations is a bit difficult for me.
Interesting note: You rotate the end cap to set the direction of rotation. My father always said that he had it apart once to repair, and he put something back out of place, so you have to turn the end cap to the right to make the driver rotate left, and vice-versa. (Apparently, it was supposed to be the opposite) I've had it apart myself, but do you think I would correct it?

I think of him every time I use it.