I recently found an old roll of film when I was going through my grandmother's effects, and was wondering if anyone knew anything about it, specifically the iso or how long to develop it for? All it says on the enclosure is Exposed Panchromatic. Made in England. And it's a little shy of 2 inches. If i had to guess, it'd be at least 30 years old, but, again, just a guess. Thanks for any help.