Does Bachmann put production date codes on their product? - No, not that I have seen.
But in the past year and a half I've been accumulating Bachmann track, rolling stock, accessories and I have noticed they do put a date code on the packaging.
Sometimes its printed (rolling stock end flaps), other times its embossed (wheels, turnout signals).
Typical is 6 digits in the YYMMDD format.
In later product it's 6 digits plus a 'K' at the beginning (maybe for Kader post acquisition).
It's interesting to buy NIB at store or online and see that "new" is actually 15 years old.