Inspected a 1973 condo today with Zinsco sub panel with 1-1/2 inch pointed screws, Yeah I survived to tell my tale. I replaced screws not for them but for my safety screwing cover back on. Anyway , floating neutrals with a 4 wire feed-aluminum. Questions are
1- They have all the copper GECs twisted together in 1 clamp with the aluminum feed GEC , I’ve seen the GEC’s twisted together in clamps before on older installs and should be on its own separate bar bonded to the panel but can 2 different metals be under one clamp, yes it had the oxide gel on it.
2- Usually the GEC clamp is attached to the panel but here it was floating - literally- but had a #12 wire acting as the bond to a screw in the panel. This # 12 big enough or size dont matter here - and only here as I’ve heard ;o)
Bonding strap was there but not attached, guess it didnt reach the clamp.