I think you might have a Gen3 RTF2 model; they can easily be mistaken for a Glock Gen4 if you're not familiar with both models.
All Gen4 models should say "Gen 4" on the left side of the slide, immediately after the model number, as shown in Butch's photo, above.
Here is a frame comparison photo, with the Gen4 at the top, and a Gen3 RTF2 right below it (click photo to enlarge it):
The Gen4 models have about 12 flat-top pyramids per inch on the grip surface:
Here is a photo of a Gen3 RTF2 assembled. This particular pistol has the curved "fish gill" type slide gripping grooves, but later Gen3 RTF2 models have the normal straight slide gripping grooves (click to enlarge):
The Gen3 RTF 2 models have about 20 smaller pyramids per inch on the grip surface:
Another quick way to tell them apart, is the Gen3 RTF2 has the pyramid gripping surface extended up into the thumb rest area; Gen4 models, as well as all other Gen3 Glocks, have smooth thumb rest areas. Check the frame comparison photo, above, to see the difference.