We list 2,779 brands. We have verified a decoding rule for 96 of them. That is 3.5%, and we would rather print the number than let you find out one lookup at a time.
There is no standard. A batch code is whatever the manufacturer decided to stamp, and the scheme is rarely published. Working one out means collecting real codes from real products whose manufacture date is independently known, then finding the encoding that explains all of them — and then checking it against codes it has never seen.
That last step is the expensive one, and it is the one that separates a rule from a guess.
Every lookup we cannot answer is recorded. Brands are added in the order people ask for them, so the queue is shaped by real demand rather than by which brands are easiest. If your brand isn't covered, entering the code is the single most useful thing you can do — it moves that brand up the queue.
Because you would act on it. Someone reading "made in 2019" throws out a product that is fine, or keeps one that isn't. An honest "we don't know" leaves you where you were; a confident wrong answer moves you somewhere worse.
Lotly