This is a vintage set of straight walled aluminum fixtures for case and crystal presses. It is used by watchmakers and watch repair people to install watch crystals and press on case backs.
Each of the dies is reversible, so in the pictures if you see the die stamped “39.0” the reverse is the 39.5 mm die. Though it doesn’t appear that the set is complete, it comes with a large assortment of sizes that covers both larger size modern watches and vintage women’s watches. (My unsolicited advice: wait until you actually get the tool to see if you really need anything else. You’d be surprised how handy this assortment can be!)