Wed Jan 04, 2017 9:10 am by MartinHewitt
I searched last night for S&Gs manipulation protection mechanisms. I came up with following interesting patents, though not all are really about manipulation protection.
Older patents
US57574, US98622, US1867001
Electronic Locks
DE000069834840T2, US5816084, US6016677, US6094952, US6196037, US6212923, US6813917, US8516863
Manipulation protection
US3170316: Mechanism in 8410
US3968667: Mechanism in 8550, 2937
US4275576: Mechanism in vault door locks 6430, 6435, 6530, 6535
US5473919: Manipulation protection by magnets on lever and cam
US5749252: Manipulation protection by wheels on cam
X-ray protection
US4776190, US4796446
Combination locks controlled by keys
US3991596, US4375159
Others
US4163376: Torque Adjustment
US4359883: Combination lock with time delay
US5343723: Miscellaneous improvements
US5502990: Key locks FAS 6860, 6870, 6880, 6890