...So I'm modeling a building from the '30s that has a bit of older gear. So the questions:

1) What do you guys do when a transformer doesn't include impedance on its label?
2) What do you guys do when a distribution switchboard predates (or at least doesn't include) rated fault current?
3)Lastly, can any of you hazard a guess the wire type in the MCCB pic below? I believe it's RW or RHW, but none of it's legible. For scale, I believe the wire in the picture is 0 AWG aka 1/0.

1. For a little dry type like that I'd just pick a typical transformer from the library.
2. I go by the ratings of the breakers in the board. Google says that ITE breaker is 10kA. If that isn't your question and you can't get any breaker data from all or some of the old breakers installed in the board I'd go with 5kA.
3. Doesn't matter for SC and therefore AF IE calcs. Only matters for ampacity or insulation voltage rating. Since the voltage is evidently 240V or 208V and voltage rating of the insulation is at least 300V not a problem there and 1/0 copper or AL at 60 deg C or higher 100A minimum ampacity is good on the 90A breaker.

One other consideration is condition of the equipment and if it's been properly maintained per manufacturers instructions or NFPA 70B. You might not be able to do an AF study that you can stand behind if you don't have confidence that those old breakers will operate like they should. Or even at all.

Thanks! All the big items are fused disconnects, so I'm not too worried about those. Some of the old branch panels use breakers I'm not familiar with, but I'm sure I can dig something up. Not sure about how reliable they are though.

When I worked at Ball State years ago they had some very old stuff like that and older. Like out of Frankenstein's lab. In the basement of one other the old Ball family mansions there were some disconnect switches still in use that were manufactured by the Colt firearms company. I looked them up and they were either great depression or WW2 era. Don't remember now for sure.