United Kingdom. A Second War Royal Navy H.M.S. Monarch Cap

Of dark blue wool, stiff frame sides, visorless with a concave top, tally ribbon in black nylon with gold-threaded stitched letters inscribed "H.M.S. MONARCH" and tied in a bow on the left side. The interior sides lined in silk with maker mark W. Acres HAMILTON, ONT., with a 48 mm thick leather sweatband, with small tag identifying the size of 6 ⅜, with elastic black chin straps attached to each side, measures 48.5 cm in circumference, exhibiting light wear and loss of elasticity in the chinstrap, remains in very fine condition. 

Footnote: HMS Monarch was an M-class submarine of the Royal Navy, originally completed late in the First World War and later adapted for specialized roles. By the time of the Second World War, she had been converted into an aircraft-carrying submarine, equipped to launch and recover a small reconnaissance seaplane for scouting purposes. Although innovative, this concept proved of limited practical value in wartime conditions, and HMS Monarch saw only restricted operational use before being paid off and scrapped during the war, reflecting the experimental nature of such hybrid naval designs.