Today in 1998, US Patent EP 0823384 A1 was issued, an invention of Baswinder Singh Dhillon, for his “Beer Keg Cap.” Here’s the Abstract:

A beer keg cap 10 comprises a continuous cup shaped member to receive the neck of the beer keg. The cup shaped member comprises a top 12 and a depending skirt 14. The skirt 14 includes lines of weakness 20 extending upwardly from its lower edge to provide tamper evidence by breaking. The cap 10 further includes a plurality of inwardly directed tabs 16, to engage under the neck of a beer keg. The tabs 16 are elongate in the circumferential direction.