A Metropolitan – City of London Police Reserve whistle. It is impressed with maker’s details - J. Hudson & Co. of 244 Barr Street, Birmingham, England. It has the word “Patent” but no patent number. CLPR – was formed in 1911 – 1919. I think it is made from nickel plated brass and has the original brass chain with hook. The whistle measures 8.2cm long and the chain (including the hook) measures 42cm long. It is in good working order with any wear/marks in keeping with age and use; unpolished with age patina. Please look at all the photos as they form an important part of the description. Thank you for your interest.