Regarding the Cno7, a close up ophoto of the serial number area along with a good photo of the back of the bolt will tell all. But yes, the guys who assemble the Cno7 rifles from parts can read so they will know the serial ranges for each year. However, a good close-up photo will almost always show the difference of the metal in the serial number area.
With regard to prices, certainly an excellent original Cno7 with accessories should fetch $1800 to $2500. New in the chest with all accessories is worth even more, although it is a curse. That is why you need to own several, so you can have a now one for show, and a used one for go.
The 1950 LB should run around the $1K mark. It is their condition that makes them worth more. The fact that they are postwar production diminishes their value slightly. The same rifle with wartime dates would be worth more.