What is "crown cork"

The crown cork (also known as a crown seal, crown cap or just a cap), the first form of bottle cap, was invented by William Painter in 1892 in Baltimore. The company making it was originally called the Bottle Seal Company, but it changed its name with the almost immediate success of the crown cork to the Crown Cork and Seal Company. It still informally goes by that name, but is officially Crown Holdings. Crown corks are similar to the Pilfer proof caps, as usage of both products is to seal the bottle.