thats for the entire range from crosman
i can ask Tom Slocum in the US who no doubt will know if the serial number can be dated
these are some of the variations in them (from a GTA post)

1) Steel vs aluminum triggers
2) Three different piercing caps
3) 5 hole sideplate vs. 6 hole sideplate (not interchangable)
4) Radial stroke of the safety & corresponding slot length
5) Length of the safety slot on the left stock panel
6) Some have the stop (p/n 90) & stop roller (p/n 92); probably coincides with the 5/6 hole sideplate thing.
7) Brass vs. aluminum valve body
8) Obviously various "pat pend" and "Crosman 600" locations on the frame
there was a great post with pics from 2004 that highlighted the marking differences but sadly the photo's aren't visible now