A friend put this on FB wanting to know if anyone knew what it was used for. My guess was that it was use to seal two thin pieces together. Any guesses?

Good guess on your part Ron...IDK...can't say I've ever seen anything like it. Obviously meant to roll with the two ball bearings in/on some type of seam?

The green handle color reminds me a lot of 40's through early 60's kitchen tools to mimic Jade green services by Fire King and some others. Common color along with red. 

 

 

What might look like a child’s marble toy was actually manufactured beginning in the early-1930s as a razor blade sharpener.

you da man Dan...

My dad told me they tried to sharpen razor blades with pieces of glass during WWII. The war effort apparently cut into the razor blade supply. Never thought much of it until now, interesting tool.

Whew!  Glad y'all cleared that up.  I was afraid it was some new married guy ceremony thing.

Guess I'm just a tad late to the party. Yes, they are used to sharpen razors. Generally, they are used with straight razors even though the graphic above shows a double edge being sharpened. I have a couple in my collection. I'm always on the lookout for these, mugs, brushes, stoops, and of course straight razors.