Ok, I had a look at the various era Sideswipes I have here and here's 
what I've come up with:
 
- Japanese Diaclone Sideswipe: 1 verical line for each foot
- Italian Diaclone Sideswipe (red): 1 vertical line for each foot
- Italian Diaclone POLICE Sideswipe: 3 vertical lines for each foot
- US Sideswipe: 1, 2, or 3 vertical lines for each foot
- US Red Alert: 2, and 3 vertical lines for each foot
- Reissue Clampdown and Deepcover: 3 vertical lines for each foot.

I think the Japanese Diaclone POLICE Sideswipe will have 1 vertical 
line, all reissues have 3 vertical lines.

At a guess I think the 2 lined ones are late prerub/early rub on 
Swipe and Red Alert? Maybe changed about the same time copyrights 
changed and the launchers for Swipe changed.

All the best- Maz