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.
When organisms die, the carbon-14 begins to decay at a known rate.
Carbon-14 has a half-life of 5,730 years so dating is limited to between a few hundred and about 50,000 years. It is also important that samples for dating are collected carefully to ensure they have not been contaminated with more recent carbon.
Radiocarbon analysis can only be used on organic materials, and is often used to date charcoal associated with campfires and archaeological deposits.
The method also assumes a 'zeroing' event in the life of the material, when it was either last heated or exposed to sunlight.
General Machine-made Diagnostic Features: Machine-made bottles will exhibit most or all of the diagnostic characteristics explained and illustrated below.