If those are the classic “Q-series” Zinsco breakers, I am fairly certain that if they were removed, you could see a row of ”braided” busbars for each half of the panelboard, with colored plastic covering over the respective busbars, except where there is a protruding tab at each connection extending into each breaker-pole spring clip.

For lack of a better description, the “woven” black-red-blue sets of aluminum busbars look sorta like a piece of flat rope.

The bus bars are plated copper,in tearing a couple of them apart for scrap I learned it is not worth the trouble,