Described on pp.180-183, the almost complete lack of footnoting to document facts mentioned in the text is frustrating.
The excellent closeup photo of the interior of the lock on p. 183 provided the following list of patent dates associated with this lock (next to the equivalent patents):
20 July 1875 (US165878)
7 August 1877 (US Reissue 7835 which is a reissue of US165878)
13 November 1877 (US Reissue 7947 which is a reissue of US195539)
25 September 1877 (US195539)
Researching the patent numbers corresponding to the dates on the lock was unnececessarily time consuming due to the lack of adequate footnoting.
Jack