Two sides of dating

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: 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.These deviations are discussed on the main Bottle Dating page in a box under 4.The statement about machine-made bottles may seem contradictory (finer but more visually distinct) but is a function of the higher machine blowing pressure.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.Be aware that bottles and jars made by early to mid-20th century press-and-blow machines do not usually have ghost seams, since the parison mold was usually one-piece, but will typically have a valve mark on the base (see #6 below). A suction scar is present on the base of Owens Automatic Bottle Machine produced bottles.This distinctive base scar is easier to illustrate than describe; click on suction scar for a picture of a typical scar which exhibits the diagnostic "feathering" that surely indicates Owens machine production (same image is below left).

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On many early (very early 1900s into the 1920s) and occasional later (1930s and later) machine-made bottles the vertical body/neck and finish mold seams are discontinuous and offset from each other; click offset seams for a picture of this attribute.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.(Mold seam thickness and how high it protrudes [height] is of only moderate use in telling a machine-made bottle from a mouth-blown bottle, though if a bottle fragment has a hair fine mold seam, it is highly likely to be from a machine-made bottle.) 3.General Machine-made Diagnostic Features: Machine-made bottles will exhibit most or all of the diagnostic characteristics explained and illustrated below.(This summary is largely an amalgam of Toulouse 1969b; Miller & Sullivan 1981; Jones & Sullivan 1989; Boow 1991; Cable 1999; Miller & Mc Nichol 2002; Miller & Morin 2004; empirical observations.) It should be noted that features #1, #3, #4, #5, and #6 are primary indicators of machine-made manufacture.

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