Welcome to the Forum..., they can be recognised by the fact they are tapered on the ends, the 'flat' on the rear is actually a 'second' ,separate piece, that is "pressed" onto the bolt body...you can "see" the outline of a circle on the back ( end ) of the bolt and there will be a 'flat' in this circle, (this flat keeps the bolt piece from actually being able to 'turn' ( pivot) on the body.....this was done during the Korean War era to "save on steel" for the war effort..instead of turning the bolt as "one piece" from a two inch diameter piece of bar stock, they made two pieces, one the bolt body from a 1 inch piece of stock and a 'piece' of flatstock as we said ""pressed" onto the end........the down side of this is they can and will "come apart" and at the wrong possible time...if you send any of these in for "service" the factory will keep the old bolt and replace it with a newer version, being "safer" to use.........
when the MK II came out ( at least in the stainless versions) , the bolt again, had this "taper" and by the
looks of it appears to be two pieces also, but it is "welded"???? ( not sure really,but there is NO circle on the back ,but you an "see" a line around the bolt body that shows two pieces...
if you have a MK I or RST from this era (eartly 50's ) and the bolt ears are tapered, it just maybe one of the two piece bolts.............
group of bolts and the one on the left is the Korean War vintage one, and the other end are the later stainless ones ,tapered and straight.......(one piece and two)
this is the rear of the early ,two piece bolt...........
hope this helps you out................