As toolmutt said, a folding spanner for pin lug style hose couplings-looks like brass which would indicate an old one. This is a small folding spanner that a firefighter might have bought for his personal gear and kept in his turnout coat. With a number that high it may very well have been used in an FDNY ladder company. 166 Truck is still an active FDNY ladder company and is located in the Coney Island section of Brooklyn
Tom B.
