Utilitarian items makes up the bulk of the bottles produced during the 19th century and first half of the 20th century. Bottles intended to be used once to dispense the contained product without much hope of return, though as noted in #4 above, many types of bottles were commonly reused during the 19th and early 20th centuries; or 2.
Heavy duty bottles intended to be recycled and reused by the producer or distributor of the contained product (primarily soda, beer & milk bottles); or 3.
Some technological changes were expensive and not adopted by glass makers until it became an "adapt or perish" issue and many glass factories just perished.Other diagnostic tools must be used to date these items.Shape is more indicative of function - i.e., what the bottle was used for or contained - but even that has a myriad of exceptions.Utilitarian items include canning/fruit jars and figured flasks since they were intended to be reused by the purchaser and have been observed to follow well the dating guidelines, though there are some manufacturing timeframe differences with canning jars.(Click canning jar to view the typology page section devoted to that category.) The beer bottle pictured to the above left is a classic example of a utilitarian bottle from the late 19th century that was typically reused.