... Oyster Perpetual means it has a waterproof case (Oyster) and Perpetual denotes an automatic movement. The Datejust has always been an automatic model never offered with a manual wind movement.
If your friend says it has a manual movement something is wrong: the movement has been changed or modified.
If you check between the lugs you´ll find the model/reference number (also inside case back) and its serial number and this can tell us more about this watch which looks like it has been polished too.
Keep us posted when you have the watch on your hands! Cheers! Abel