This is a vintage, unused/unfinished production casting of the later Mk VI tricorder seen in the series. Complete with hand scanner (cast off screen-used). This was the precursor to the Mk VII tricorder, the Science version of which did away with the separate hand scanner. Body made of vacuum-formed styrene with a vacuum-formed door, just like the screen-used originals.
This one, in fact, is an extra pull the Prop Dept. simply never finished for screen use, so is the next best thing. Last two pics show side-by-side comparisons to the earlier Mk VI and later Mk VII tricorders. Requires basic hardware (hinges), screen-accurate graphics and accurate automotive paints to finish.