A nice little older 6-inch duplex trig rule. The older Picketts had much nicer cursors than the later models. It's hard to see in this picture, but this Pickett, like most i've seen, has holes drilled in the ends of the slide. I haven't been able to figure out what this is supposed to achieve. Ventilation? So you can use your slide rule as a keychain? Maybe so you can thread a string through the holes and wear your slide rule around your neck? To make it possible to grip the slide with a bent paper clip, facilitating slide movement? The world may never know.