At one time I shoot a lot of slide film on available light photography [starting 1963]. I would always use a tripod if the shutter speed was slower the 1/[lens focal length]. I have shot a few rolls of 3200 film at the box speed with 120 film, but I do not have enough experience with it to discuss it. That aside, I have used the Jiffy Night Calculate since it was first published in 1963 in Popular Photography.
This image was shot on a 35mm camera, at 10pm, and metered normally for the box speed of ISO 400. 1/8 sec f/1.4. The focal length was 35mm, but I don't think I could have gotten it without support: I had my elbows firmly placed onto a pier rail.
Without support, I find the 1/focal-length rule to be quite reliable for me, with decent success rate at double that. But that's only true for 35mm format. My handholding record is quite miserable with MF cameras.
@CMoore Thank you, that's a legit question. I meant the in-camera meter's defaults (center-weighted) set to box speed. No exposure compensation. No meter+recompose.
I've gotten away with delta 3200 at night (street lamps) sometimes. A lot of the time I used 1/(2xfocal-length) as the minimum shutter speed with the lens wide open.