Hello, all, especially those vendors of Master Lock Company products for many years. Does anyone know when Master Lock modified the innards of their 1500/1525 locks such that a steel spring/band returns the bolt/plunger assembly to the locked position when the shackle is raised? The older design (available in the 1960s up to ..?) used a cam coaxially mounted with the disc tumblers to achieve this action. I think this also coincides with redesign of the tumbler discs such that the last number of the combo cannot be conveniently discovered by pulling on the shackle while turning the dial. The older design is easily identified by the knurled silver knob on the rotary dial.
I've done a patent search at USPTO but only came up with patents on Soref and Foote's original "permutation" key/combo lock designs (assuming Master patented the modifications). Thanks for your time and comment. Sincerely,
John Wood (Code 5550) e-mail: snipped-for-privacy@itd.nrl.navy.mil Naval Research Laboratory
4555 Overlook Avenue, SW Washington, DC 20375-5337