I believe that patent is for the 4 sliding bolt system was used on the larger model Briggs safe. One turned up on Ebay several years ago in, I think, New Jersey.
This is a picture of it.
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My Brigs is smaller and has 2 sliding bolts. The Briggs expanding bolts are on the back of the door where the Bates looks to be mounted in the center. Probably a more secure design. On this Briggs, the expanding framework slides into a grove in the door jamb and that in of it’s self is probably quite strong. The weak link in my opinion is the size of the bolts that secure the sliding bolts. At about ¼″ (they are of an odd size and thread) and the fact that the head is not much larger than the slot it fits in, I think pressure would cause them to fail either from severe prying or explosives. Although a very tight fitting door would make that difficult.
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