Any ideas why a breaker would be wired back on its bus bars?
Thanks.
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Split Bus Panel
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Yes Chris nailed it a split bus panel. The 60 amp circuit breaker feeds the bottom portion of the panel via the two blue conductors. Those conductors are factory welded or soldered to the bus.
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Given that there was no main shut off, you could still shut off the lower portion of the panel with that 60 amp? But the breakers north of that would stay live. Gotcha. Not sure what the reasoning would be behind that but I guess that’s another reason to replace federal Pacific panels.
Yes that is correct. The upper bus is usually fed directly from the meter and cannot be shut off. Another reason why these types of panels are pretty much obsolete.
A split bus panel used the up to 6 throws of the hand as the mains.
There are probably still millions (if not tens of millions) of split bus panels in use today and there is nothing wrong with the overall design. FPE panels are hazardous yes but the fact that they are split-bus does not add or take away from what the problem is.
Sorry for the newbie question but what would be a practical application for this? Would it be someway to isolate the circuits in a sub panel and run them using a generator so that you don’t back feed the main ? For example if your sub panel fed a separate room on your property, you could then run the main panel with one generator and a sub panel with another?
I’m not sure what you mean by “this” but am assuming you mean the 60A 240V sub main? I don’t think it was ever setup this way for use with a generator. At least not that I’ve seen in my area.
Split-bus panels (again, in my area) typically have the 240V loads up top (no more than 6 switches). Usually, there are 4 or 5 them up top - water heater, dryer, range, A/C and sub-main would be a common example. The sub-main is all of the 120V loads in the house. So, all of the lights and outlets.
Why panels were wired this way is a good question but the same can be asked for all kinds of things we did back in the 60s/70s (asbestos, lead paint, bad hair styles, etc 
). I’ve actually had split-bus panels in a couple houses I’ve owned and generally don’t mind them but they are physically small inside and hard to work on.
The main thing I watch for with these panels is that the six switch thing hasn’t been messed up and I’ll often try to explain to the buyer how the panel works since there isn’t a single main breaker. Honestly, the six switch thing is totally an arbitrary number. It was limited at six as that was just thought to be a max number of switches that someone could flip quickly (not sure about you but if there were sparks flying from the wall and/or the house is on fire I could flip even 20 breakers pretty damn quick).
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Larger main breakers were expensive. Several smaller breakers were used in place of one large breaker for the whole panel. They fell under the 6 throws of the hand rule.