Without getting too exotic, the Columbus tubings of the period were:
SP - road, heavier walled double butted
SL - road, lighter walled double butted
PS - track, heavier walled double butted
PL - track, lighter walled double butted
There was quite a lot of difference between the SP and SL (and between the PS and PL). The PL wasn't good for much other than ultralight pursuit frames or the occasional hour record bike. The SL worked for smaller frames and for lighter riders, but was fairly common on road frames in all but very large sizes. All in all, there just weren't many alternatives to select from, so tubing choice was pretty straightforward.
Each tubing evolved somewhat over their lifetime, so particular steel composition and precise butting tapers, wall thicknesses, etc. changed a bit, although the feel generally stayed about the same.