Lozenge decoded: 25 May 1871. Jenny Thompson (p. 107) reproduces the handwritten record, and it appears to be "John Harry Wood, 25 Baker Street, Portman Square" (followed by a squiggle that might be shorthand for "London"?). If so, it's not far from what is now Marble Arch and the Wallace Collection (as well as the legendary apartment of Sherlock Holmes!). Perhaps some Holmes on this board can tell us all about John Harry Wood!