I had one for the 9 volt AM/FM transistor radios back in the day... remembering the Panasonic transistor radios (I think before integrated circuit chips!), pocket sized for when on the move. But disposable 9 volt batteries got expensive so the eliminator came in handy when I could plug it into AC.
Yep,
Back when RadioShack had the "One Free Battery per Month" club card, the 9 volt cell was by far the most requested size for the free battery!
The two stores near me would run out of 9 volt cells the first few days of each month.
I also had a battery eliminator but it was custom made for some old video camera or digital camera I had back then. Being made by the manufacturer of the device, it had a proper entry for the wire to exit. I don't think I ever used the thing but I remember it came with the camera which was probably a bargain when you look at how much some manufacturers get these days for custom AA cell battery holders to be used in place of the Lithium battery pack when it has ran dead and you are out in the field.
I had another one that also took AA cells or you could use an external supply plugged into the devices barrel type power jack. I'm thinking that one was from one of the amateur radio manufacturers for some old portable but not positive.
