Should I accept 2,5 year old Samsung Galaxy replacement battery?
Comparing confirmed Chinese translation of these four symbols (yes -- it is a manufacture date) with Izzy's answer, which states, that Li+ batteries have a self-discharge rate of approximately 5–10% per month, we end up with conclusion, that even with most optimistic scenario, Li-Ion batteries stored in store or warehouse without cyclic re-charge (which most likely never happened) are completely dead after 20 months at most.

Which is equivalent to less than two years. Which leads us to a conclusion, that 2,5 half year old Li-Ion batteries are completely useless and shouldn't be purchased nor used.