In 1905 they added a hardened wear plate. Then in 1910 the whole bolting system was redesigned in order to reduce parts and at that time a hardened wear plate of a different design (stepped) was used. This design was used until the end of Parker production.
The original design of bolting does wear over time. The tapered bolt design is good, but does not hold up over time as well as two hardened surfaces used for bolting. That is why the 1905 design was implemented so that a hardened and replaceable insert was being used. The 1905 design however used more of a straight bolt design.
The stepped 1910 design combines the benefits of all 3 into one. A tapered bolting surface, a straight surface and a hardened replaceable piece.
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B. Dudley
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