Dating Bottles with the The concept is that the higher the side mold seam on the bottle the later it was made - at least in the era from the early to mid 19th century until the first few decades of the 20th century.
How do you date beer bottles?
There is no industry standard as to how brewers date their beers, though most use a “bottled on” format. That style indicates when a particular beer was canned, rather than when it is best by. Often, that date can be found on the bottom of cans, on the side of bottles, or on the case itself.