1800s expression for dating
In short, there was (and is) nothing to stop a glassmaker from using an obsolete method in the production of a bottle.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.Of course, soda & beer were reused up until quite recently.
When a likely or known "older" item is found in a known "newer" site it is referred to as deposition lag.An example of this is the finding of a few pontil scarred utilitarian bottles among otherwise late 19th or early 20th century refuse.It is unlikely that this bottle was made during the same era, but instead was reused for a lengthy period or otherwise retained until broken or discarded.This bottle dating "key" is a relatively simple "first cut" on the dating of a bottle.While running a bottle through the key questions, the user is frequently directed to move to other website pages to explain diagnostic features and concepts as well as to add depth and/or precision to the initial dating estimate.
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.