Extremely rare Chelsea 12 inch pilothouse clock, movement number: "177792" which is stamped Chelsea Clock Co. Boston U.S.A.. The clock has a 12 inch engraved silver dial with waxed Arabic numerals and has the engraved signature below the winding post which states “CHELSEA CLOCK CO. BOSTON U.S. A. . Below the numeral "12" is a large second bit which is engraved: "NON-MAGNET".  To the right of the second dial is a slow/fast adjustment. The clock retains its yellow brass case with hinged bezel.  (CL-572) 
Note:  The non-magnetic feature allows the clock to be near large machinery like steam engines.
Reference:  Dementer, Andrew C. and David D. Dementer, "Chelsea Clock Company: The First Hundred Years", 2001.  An almost identical 12 inch pilothouse clock appears on both the dust jacket cover as well as the frontispiece to this book.  
Condition:  The case has been recently polished and lacquered.  The dial has been resilvered.  The movement has been recently overhauled and is in good working order. 
Dimensions:  Diameter of Dial 12 inches, Diameter of Bezel 14 1/4 inches; Depth 3 3/8 inches.