Old Penn senator rod letter meanings

[Dpp61]

I'd like to know what the different letters mean on some old Penn Senator Rods I've inherited.
Difference between S 3260 RF 40-60lb 6/0 Penn Senator Road and the 3165 ARW 6/0 Penn Special Senator DL 40-60lb
Difference between 3140 RW 4/0 Penn Special Senator 30-50lb and the SS-3140 RW 4/0 Penn Special Senator 30-50lb

Thanks in advance to any of you Penn fishing