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"Is one of the sets of dimensions for a case?The objective looks like a 1-1/2 inch by either Smith and Beck or R. and J. Beck of London, not a Charles Spencer product. If purchased in 1856 the microscope would have been made with Spencer's bayonet mounting system for the objectives. The Beck lens would have a screw thread for mounting. I believe this lens has been forcibly screwed into the bayonet socket.Speaking of Spencer microscopes, I see no mention in the search results of the C. A. Spencer and Sons for Geneva Optical Works mentioned in the journal Rittenhouse, vol. 2, No. 3, 1988, page 77."