Mine has finger grooves but no rail.
The 26 and 27 are subcompact. The 30 is about the size of the 23 and 19 and is just called a compact.The Glock 29 and Glock 30 subcompact models can have a rail.
Gen 1 no rail no finger groves, gen 2 finger groves no rail, gen 3 rail and finger groves, gen 4 will be marked gen 4 and have interchangeable backs straps at least on the full sized model. That's my understanding anyway.
Can anyone tell me the difference between a G36 gen 2.5 and gen 3?