What the heck is this?

Way back when, many a homeowner had one of those tools.
Yep, and a box of the little push in spikes that held the glass in place while you puttied the perimeter of the window back. You also had to know how to get the sides of the window frame off to put a new rope on the weights that held the window open, after the old rope rotted in two and the weight fell into the bottom of the window frame...lol. Ah, the good ol days. :)