This is a cutter iron for a Stanley No. 45 & 55. It is a No. 5, which is a match.
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Shallow Impact Socket, 1/2-Inch Drive, 6-Point, Metric 17 mm
Single shallow length, 1/2 in. drive, 17 mm size socket. Trusted by professionals, the high performance sockets are what you need for the job at hand.