Thanks for the explanation Nomad. I’ve just purchased some expired Fuji NPS 160 to just have a test of the camera. What sort of light condition would be ok for this speed at the estimated shutter speed and apertures, I know that sounds like a daft question but I have no idea and sounds like you would know lol
Short answer: Wing it.
Pragmatic answer: f11 for cloudy to hazy sun, f16 for sunny and very sunny.
Techy answer: Get a light meter.
Long answer...
Have a look at the NPS 160 datasheet, part 5...
https://www.fujifilmusa.com/shared/bin/AF3-809E.pdf
That's an adjusted sunny 16 exposure guide. It's adjusted because the film speed is 160, but cameras don't normally have 1/160th as a shutter speed, meaning you can't apply a normal sunny 16. Instead, they say to use 1/125th, which means a slight over-exposure, and the apertures are stopped down a bit to compensate, such as f16 and 2/3rds for sunny, instead of f16. (I make that a slight under-exposure overall.)
You need to adjust these apertures to work with your shutter speed, or choose the lighting conditions to match the exposures your camera is capable of. To make it easier to work out, I'd tweak the exposure guide by changing the shutter speed to 1/100th and stopping down another third of a stop. In other words, for cloudy bright, 1/100th at f11 is almost the same exposure value as 1/125th at f8 & 2/3rds. Choosing suitable light now becomes a bit easier - you have whole stops and a 1/50th shutter. If you used the now-tweaked exposure guide's 1/100th at f11 in cloudy bright, you'd over-expose one stop - but you'd be about right if you stopped down to f16.
That's for exposing at box speed (near enough). In reality, some guesswork is needed. Expired film loses speed, the speed of your shutter is a half-guess and it could be inaccurate anyway, and the stops might not be accurate either (the middle stop in my No2 Brownie is quite a bit out while the other two are pretty close). However, guesswork isn't too big a deal because the film should be quite tolerant of inaccurate exposure.
In short, even if you were to nerd out and try to determine 'correct' exposure for the conditions (or choose appropriate conditions for the available exposure values), the chances are that something is going to be out of spec anyway, and even if it is, the film will probably mask it. Hence the short answer above.
Finally, I agree with everyone that says to get some Fomapan 100. Cheap, cheerful, and the formulation is straight out of the 50s.