Amazing to notice how narrow the engine nacelles are! What particular type is this?
Boeing 707-320 series. The engines are Pratt & Whitney JT4A turbojets. The version was quickly superceded by the 320B which had first generation turbofans - P&W JT3D. Some 320 series aircraft were re-engined with the later type but others found there way to second-hand market and carriers such as Donaldson.