Most produce you find at larger grocery stores, have stickers applied before they arrive to the store. Nobody there gets paid enough to care if the apples all have their stickers (or bananas, or pears, or - insert food item here)... So many are fairly standardized.

I'm not sure where in the production and distribution chain that the stickers end up on the produce, but it's before the stores.

I worked produce department for a few years when I was a teenager, and we got shipments from our own internal distribution, and the manager would suppliment anything they couldn't provide with a smaller, more local distributor. AFAIK the local guy had more reliable stock, but cost more (not enough to create a loss, as far as I was aware - but enough to reduce profit margins); so the thinking was: get it cheap from distribution, if they can't or won't, then fill in whatever is lacking with this other guy. It was almost always the same stuff regardless (in the same boxes, from the same growers, etc) and everything from both sources always had the exact same labels/stickers/codes on them. The workers only needed to get it from the truck to the shelf for the most part. The only produce we touched any more than that, was the stuff that went on the wet display; mostly lettuce, celery and such.

I've worked at several stores and I've noted the few codes that I actually know are consistent among different local stores.

IMO, it might change from country to country or something, but largely, the numbers are the same.