Those are known as U Press It cans. If you look on the lids that is what they say. Once the seal is removed you push in the top center of the lid and it opens with a pop.When you want to close it, you squeeze the sides and it closes. Probably 60's vintage, and unless they have really been stored wrong the powder is still good. I have several pounds of powder in those an am still using it. Unbeknownst to most single and double based powders have a shelf life of 50+ years.