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.
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.
)Reuse, of course, does not change the manufacturing date of the bottle itself, but care must be exercised when using the known date of one or a few bottles to date other items found from the same context.
When a likely or known "older" item is found in a known "newer" site it is referred to as deposition lag.
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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.Pontiled base fragments could also be from later produced "specialty" bottles which are described below.5.Some bottle shapes are indicative of a particular manufacturing era, though many bottle styles/shapes were used for so many years - like the cylinder whiskey "fifth" or square snuff bottle - that the shape itself is not indicative of age.A NEW IAOS PUBLICATION: A new obsidian-related volume, Twenty Five Years on the Cutting Edge of Obsidian Studies, has recently been published by the International Association for Obsidian Studies (IAOS).To have a look at a sample or to buy a copy online through Pay Pal, click HERE.