I found this item at Pacific Ocean market. The package had been opened. I didn't see any others there.
Yes, it's a melon-seed splitter.
In China, roasted melon seeds are a popular snack, and are enjoyed much the way many people enjoy sunflower seeds here. You split 'em with your front teeth. Some people eat so many seeds that they wear a little groove in a front tooth.
But I guess if you didn't have teeth or wanted to save your teeth, you could use this. It comes with handy instructions.
But can you imagine how slow and tedious it would be? Takes all the pleasure out of snacking.
(Click on the "silly gadgets" tag below to see other examples.)