The rifle your father is holding is not an Enfield. Although the name Enfield is often used for that rifle but it is not an accurate description. It is a M1917 using the US nomenclature. The history of the rifle is this. Prior to WWI,the British were thinking of introducting a newly designed rifle to replace their Enfield SMLE. Tests were done and they settled on the Enfield Pattern 14 rifle. But then the war broke out in 1914 and it made no sense for them rearm during war and they went full capacity to make the SMLE. But they were short of rifles, so they took the P14 design to America and had several companies start to make it in 303 caliber for shipment to Britain. But when the US became involved in the war they too discovered they were short on rifles so the instructed the companies making the P14 to stop, retool it for the 30-06 cartridge and that rifle became known as the M1917. There were more M1917's used in WWI than the 1903 Springfield rifle. So, calling it an Enfield is a reflection of its origins but not its proper Model name. I hope that helps. More info can be found http://en.wikipedia.org/wiki/Pattern_1914_Enfield