I agree that the "search" tool should be used more often, however, the age of an SKS is no trivial matter.
For us collector's, the year of manufactor could make all the difference. Think of the Soviet produced SKS, the one that started it all. It sure make's a big difference whether it was made in 1949 or 1950, and it can be the difference of a singe day coming out of the factory.
Even with less collectable variants like the Yugo M59/66, or a /26\ Norinco, the year of manufactor means something to us. It's like knowing how old your friend is, you can maybe imagine where it's been in life. It helps us to get to know our rifles, and streghtens our connection.
That being said, I only know the age of my Russian and Albanian.. hey, anybody have a database for M59/66 serial numbers?