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Unknown #4


Front Rear
Front Rear

Technical Details

I acquired my Unknown #4 from Bob Elron at the 2016 NSS Convention.

The Unknown #4 is 122 mm. tall, 66 mm. wide, 25 mm. thick, and weighs 450 g.

The Unknown #4 is made from a number of plated steel stampings and minor parts. One 2.5 mm. plate forms a 3/4-circle rope channel, and extensions tabs on the sides are bent to support the cam axle pins. The tabs expand ourward between the two pins. There are two cams, and two dimples in the shell, one opposite each cam. Each cam is made from two steel stampings riveted together. One 3 mm. stamping is folded to form the two sides of the cam, and a 5.5 mm. stamping forms the center. Each cam has 8 V-shaped notches on the side stamping, forming 9 teeth on each side of each cam. The center cam plate also has 8 V-shaped notches forming 9 teeth, but these are not alighed with those on the side. The cams are connected by a 2.2 mm. stamped channel with a stamped knurl pattern for better grip. The connections and cam axles are all rivets. Springs on the channel pivot pins act to close the cams. A 4.9 mm. stamped eye with a 25.7 mm. hole pivots from the pin connecting the channel and lower cam. This is the tie-in point.

One side of the shell is stamped with "5M," "J/A," "H2," "ANSIZ359.1," and an up-pointing arrow labeled "UP."


Thue Unknown #4 is virtually identical to the Ace Metal Products FP-7202G-3-LG-2-1. Aside from the markings, there is a minor differeince: the spine of the Unknown #4 connecting channel has a "fishscale" pattern instead of the "diamond" pattern on the FP-7202G-3-LG-2-1.

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