Depth gauge (nose) file.
Shop I worked for (early 1980's) used to sell them.
I've still got one. Worked well until the mice got in my tool cabinet and pissed around it.
You have to watch and not roll the file towards the cutter or you can make a funny shape of the guides.
You can actually make a notch in the top of the depth guide if you roll the file too far back.
The only marking on mine is this double "c" with the bar connecting them. Not horseshoes, just two semi-circles and the bar connecting them.
Tang looks to be dip painted with a pale pastel green.
Finish was a bit coarse looking on them but the teeth were good.
Wouldn't mind having a couple more, but just haven't bothered to hunt for them.