This instrument was between 1873, when Elliott Brothers began using this form of signature, and 1916, when the firm became Elliott Bros. (London) Ltd. Unlike American levels of the period, this one is provided with a magnetic compass. The floating ring that holds the compass needle is made of aluminum, graduated to 30 minutes, and read against a pin outside the compass box. This level was probably used or repaired in California: a label in the wooden case reads "John Roach, Optician, 129 Montgomery Street, San Francisco."
Ref: Elliott Brothers, General Illustrated Catalogue, with Supplementary Lists, of philosophical, Optical, and Mathematical Instruments (London, ca. 1867), p. 4 and Fig. 5.