Maybe a Kat Eyz capo, stainless steel, with the larger knob?

Could be the shubb fine tune or G7 heritage capo. Those have larger than normal knobs.

Looking on Sweetwater there's a Shubb and a G7th banjo capo similar to your description. D'Addario makes a great guitar capo like the Paige but there banjo capo is different.

Check Elliot also.

It really sounds like the G7th Heritage. But not sure if they were being made “years back”.

Here’s a pic.

The OP says it had an adjustable nob about as round as quarter. That’s rather large for an Elliot . That’s rather large in and of itself ,but the more I think about it the more I like the idea , as convenience to tuning.

Thanks so much guys. I appreciate the responses. For some reason, I seem to remember that the rubber sleeve over the string bar was square instead of being round. Maybe I'm thinking about something else. Does that strike a memory from anyone? The neck pad on the back side of the neck, was also round, like the adjustment knob. This was a classy looking capo. I can't imagine my friend back then paying the price for a G7 though. They are pretty pricey. I'll come across one of them one of these days. I did order a Shubb Fine Tune in stainless earlier today. I'm curious to see how well it works. I think that I may do a re-fret on this neck that I've been working on though. That may be causing some of my tuning issues. The frets are kind of large. In my mind banjo frets should be pretty small to keep the strings from bending too much when using a capo. They need to be almost like mandolin frets. Again, I appreciate the help on the capo. I'll keep hunting.

As far as the large adjustment knob, it did make it very nice as far as tuning. I remember how much he liked that capo. He used it on a RB-75 that he played back then. That was a nice banjo. He had several banjo's throughout the years but, that RB-75 was the best sounding one that he ever had. It was a very nice banjo.

Except for being made of stainless steel, you seem to be describing the old and excellent Ptacek capo, which I have for both guitar and banjo -- in BRASS.

It has the little bird logo stamped in it. The adjustment screw has the largest head of any capo I've ever seen, although not quite as big as a quarter. The pad that touches the back of the neck is nearly circular. Flip down latch on the square bar.

I've never encountered anything other than brass though.

It's a very good capo if not quite as elegant as the Elliott.

You seem to be describing the old and excellent Ptacek (Czech) capo. I have two, for guitar and banjo, in BRASS. Never saw one in SS.

It has a little bird log stamped in it.

Good capo, if not quite as elegant as an Elliott.