Three generations, technically. The first EL's (pictured on the right) had a real slow speed focus knob, which was later updated to "fast focus" (no difference in appearance). Latest incarnation is the Swarovision/SV (pictured on the left).
With Swarovski, you can take the first two digits of the serial number and add 30 to it for the year of manufacture. If they're the "older" EL's, about $200.00 overpriced, IMO.