I bought a bunch of electronics in a purchase, so I wound up with lots of components I didn't expect. I could identify all of them except these 4. I have 4 little cylinders. Two are stamped "12" and two are stamped "13". Judging from the misalignment of numbers they have been hand stamped. The cylinder appears to be some sort of aluminum material. The device has six pins on the bottom.
They were in a bag labeled "Fuel Cells" "03015-005"
What are these things? Is the package type standardized?