A small portion of my negatives - these are from the 1970s.
View attachment 424177
No budget back then for contact sheets.
When I started to digitize film images, I assigned a file number to each image which references a roll number and the associated frame number for that image.
Different digital versions of the same negative or slide have a letter attached to the frame number, plus potentially some useful additional info.
For example, this is 45d-2025-04-12-res 1280.jpg:
View attachment 424178
I have over 13,000 digital images, with the majority being scanned from film. Most of them are 2010 or later, but the oldest are from the 1940s.
I have many, many additional rolls of (never digitized) film where the reference prints have date and frame numbers imprinted on the back.
ALL OF MY filing and recording systems depend on the frame numbers.
And I know many others whose systems also depend on frame numbers.
I also have done printing for others, where the communication between myself and my "customers" was entirely dependent on frame numbers.