differance in Glock generations??

is there any easy way to tell the differance in the differant Glock generations? if so what are they?

First gen has "snooth" grip area (pebble grained). Second gen has "checkering" areas on front and backstrap. Third gen has finger grooves and light rails.( Some third early third gens do have finger grooves but no rail, these are sometimes called gen 2.5 by people.)

how is value effected by which generation? early generations more or less valuable than later?

http://people.aero.und.edu/~peske/framegens.jpg

Here is a good pic of the different generations. I THINK the newer ones are worth more, but I'm not sure.

As to a used Glock, there is no significant difference in used prices from one generation to another. YOU may pay more for one than another perhaps because you want finger grooves (thereby requiring a Gen 3), or prefer not to have finger groves (therefore wanting a Gen 1 or 2). The key to value is condition, not generation.

It is true that the long slide G34 and G35, or G17L command a higher price used, but that is not due to any generational issues; also, the full size big boys...the G20 and G21 are usually more pricey used (as they were also when new).