I often see a marking like the following pattern on the top of radial PTH elcos.
What does it mean? Is it an identification of the manufacturer?
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Here's a (somewhat artistic) video of those features in action.
The first two events (0:00, 0:03) are what happens when the stamped features do not work, but all the subsequent electrolytic capacitor failures (0:14, 0:16, 0:18, 0:34, 0:36, 0:39...) rip the case open in a relatively safe and controlled manner, notably not causing shrapnel to fly around.
They are strategically weakened parts of the casing which will bulge upwards and help the capacitor release hydrogen and/or electrolyte. They work quite well. Don't try this at home, but if you blow up an old capacitor with no release vents it will explode violently sending electrolyte and alfoil flying everywhere. The vents are designed to prevent such a catastrophic failure from happening.
It's interesting to see how different manufacturers have different vent patterns. It might be due to cost - most have four vents in a cross/plus sign fashion, but some cheaper ones have only two or three. It might save some money on the production line to score only two or three times. And some smaller ones have no vents at all. That's probably another question, though.