I could be wrong, but if I remember correctly the slides rollmarked special combat were never actually matched to a frame. They were sold as parts and were popular to pistol smiths and builders for building race guns in the days of "combat handgunning" (70's- early 80's).
As far as what series it is just lock the slide back, turn the gun upside down and if you see a hole in the bottom of the slide with a little spring loaded plunger in it ( the rear portion of the slide that hangs over the hammer) it an 80. No hole and its a 70. I'm doing this without a 1911 in front of me so I think you should be able to see the hole with the slide on. If not remove the slide from the weapon and check.
