The AT-84 pistol, a development of the Czech CZ 75, that had been developed in Switzerland by the ITM company who later went out of business.
Instead of the locking lugs and recesses milled into the barrel and slide of other Browning-type weapons as the Colt M1911A1, Browning Hi-Power and CZ 75, the P220 variants (and many other modern pistols) lock the barrel and slide together using an enlarged breech section on the barrel locking into the ejection port.