Had a plane like that years ago. Had about 20 narrow blades in a canvas pouch. I believe it was for putting edge designs on planks. Not just tongue and groove as Ryan mentioned. Never did use it just admired it.
I’ll have to keep an eye out for the other half. I actually found all the parts in 3 different piles, but recognize what each of them were when I saw the plane block. So I went back through and found them all.