You may think I'm being a jerk, or pedantic or such, BUT..
Because of our wheel size combination (15/18), it can be difficult to get a rear white wall tyre, AND a matching front. OR, difficult to get a front, and a matching rear. I've looked into it. I'm settling on Dunlops - info supplied by Piper, refer Dulop web site K177 front, K555 rear.
It pays to actually "see" the tyre, as my local dealer came close to ordering me some White Walls that actually had a SMALL white band around them - not what I wanted! Yet the tyre was designated a "White Wall"!
From my research, some manufacturers abreviate as follows
BW-----BLACK WALL
WW----WHITE WALL
WWW--WIDE WHITE WALL
NWW---NARROW WHIE WALL
RWL----RAISED WHITE LETTERING
Again, if you can see them in a catalog or on a bike first is the way to go. I HOPE I'VE HELPED?