The building this was the main for was gutted in Feb '03, a little over 2 months from when I took this photo. The line side of this 'main' (buss thru back to xfr vault). 'Vault' was determined to be POCO owned, with pots that had a PCB issue. BTW, it was a FPE disco, and the fuses seem to be 'original equipment.
We had many discussions on the rated capacity of the parallel fuses. This being the only one I have come upon.
Tesla, yes it is 120/208 Y, and I think it dates back to the early 1050s. Occupant was a two story, department store that was the original occupant of the bldg.
The electrical distribution, panels, & majority of the wiring looked like '50s, except the IG panel for the POS equipment.
Alas, it was all gone; I found this pic in my files. Posted it to get some discussion going.