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the suction scar on the base (point #5 above and picture to the left) can date no earlier than 1905 and are usually post-1910.
Though patented and first used to a limited degree in 1903, the first Owens Automatic Bottle Machine licenses were granted to other manufacturers in late 1904 making 1905 the effective "beginning" (i.e., terminus post quem) date for bottles with all of the above listed machine made diagnostic characteristics (Miller & Mc Nichol 2002).
In the glassmaking trade, these seams along with the side mold seams within the finish or just below are referred to as "neck ring" or "neckring" seams since they were formed by the separate neck ring portion of a machine mold (Tooley 1953).
: There are a few machine-made bottle types (milk, shoe polish and small ink bottles) or post-production processes (fire polishing) which exhibit mold seams in the finish/upper neck that deviate from the descriptions in points #1 and/or #3 above; these bottles may appear to be of mouth-blown manufacture.
Click on the picture to the left to view an illustration which shows both of these seams or click machine-made finish to view an image which shows well the seam below the finish.
Both seams are quite diagnostic of machine manufacture and are usually visible, though the seam at the top of the finish can be hard to see on some bottles - especially if the finish was fire polished.
While some collectors of antique glass purchase these delicate objects for display purposes only, others buy vintage glassware to use for cooking and serving.These are faint, somewhat wandering, hairline seams which if present (usually) are sporadically visible on the sides of machine-made bottles.The ghost seams are caused by the parison mold parts and if visible enough will be "attached" to the vertical seams in the finish.Earlier machine-made bottles (1905-1920s) tend to have somewhat thicker/higher mold seams than later machine-made bottles due to the increasing precision in mold machining and machinery in general as time progressed.Most machine-made bottles have mold seams about the thickness of a hair while most visible mouth-blown mold seams tend to be several times as thick, higher, but more rounded.