Yugoslavia 20 para KM#45 - variants ?

I dont see any comments about variants at page:

N#2001

but seems like there is a small diference between years: 

Big 20 on left. Small 20 on right. Also “A” or “R” in PAR 

Because there aren't any. You find a difference between a 1977 and a 1981 coin. Of course, they are minted with different dies already (77 versus 88) so of course they are different. A real variant can only be found inside the same year. Important type variants (in different years) should have resulted in another KM sub-number!