There are technically 3 generations. First gen has the cone shaped battery cover. I don’t believe they made any tan Gen 1s, just black. The G1 didn’t have any stops in the magnification throw lever track, which was the primary cause of the POI shift complaints. It also didn’t have the mounting bosses for the saddle mount. Mag lever and QD mount levers were on opposite sides from all other newer models. I’d stay away from G1 models due to this.
Gen 2 added the stops to the mag throw lever track. Also added the saddle mount mounting bosses. G2 kept the same “block” like protrusions in the body where the demagnification prism rotated.
Gen 3 is most easily discernible by the more rounded prism protrusions in the main body of the optic. Initial versions kept the 1/3N battery type. At some point, they upgraded the electronics and moved to a 2032 battery. This doubled battery life, IIRC, at least according to the manufacturer published specs. Battery cap is the easiest way to tell the difference between these two models.
Gen 1 models are usually fairly cheap when they come up for sale, due to the issues they had with POI shift. They are rare, though, so there’s a good chance you won’t find one for sale.
Tan Gen 2 models typically go for a premium due to cloners. They are also rare, so you will likely have a hard time trying to find one.
Gen 3 can be kind of all over the map. Commercial models typically aren’t too expensive. SU-230 models obviously command a premium. If you’re dead set on an Elcan, I’d hold out for a 2032 model as the electronic/battery life upgrades are worth it.
If you’re not dead set, I’d look somewhere else in the LPVO world, the SpecterDR is getting very long in the tooth in 2024.