Thanks for posting the question. You brought back memories of when I was back in business and Bryant panelboards and I believe they had the "quads" as well. I think I even used a couple here and there, if memory serves me correctly.

Quads were also popular in split buss panels. In the top half when people added central air.

I know it was wrong back then also, more that six devices, but that is what people did to get out of installing another panel or a sub panel.

I remember those well, even installed a few, never liked them much, felt like cheating the system

I know what your saying.
And of course it was only a murray breaker available for quads.
And some old bulldog ge breakers.

So out comes the hacksaw, sidecutters and etc to make it fit on the buss.
I wonder how many have failed over the years due to modifying the breaker to fit.

Many years ago it was thought that the mark of a good electrician was one who could make things work. Like making breakers fit in panels where they were not designed to fit in. And I did it myself.

Back in 1987 when I became an electrical inspector for The New York Board of Fire Underwriters I learned that this is not proper. Now when I teach at my seminars, I tell everyone that the mark of a good electrician is one who reads the directions, and the manufacturer's label.

I think that those of us who worked in the field, all did some things that at the time seemed clever and inovative and as Mike said made us good electricians able to adapt to adverse situations, but looking back are things that we as inspectors now know are unacceptable practices