Please note the official change of the title of this game, it is no longer "what is this".
Here is the item:
I suspect someone will know what this is. Honestly, I didn't figure it out right away. However, I have found that the readers as a group generally are more knowledgeable than me by myself.
Oh, I don't think there is really much description to add here. I included a meter stick for scale.
P.S. How come a device for measuring temperature is a thermometer and a device for measuring electric potential is a voltmeter? Shouldn't the meterstick be called either a length-meter or a meter…