What's it?

Here's a little puzzle to keep you busy this rainy Saturday... I purchased this vintage piece the other day and have absolutely no idea what it is! The holder is brass, about 10" long and is embossed with various letters where the holes are for the pins. The larger pins themselves are 6" long, very thick and have corresponding embossed letters on the heads. The smaller pins on the bottom are 4" long. The seller sold it as something that was used at a public swimming pool locker room... but the pins are way too substantial to be used for this. I know pins like this are (or were) sometimes used in the military for marking and identifying laundry... but why such large, heavy duty pins? Any ideas out there?