<<What is the significance of the white stripe?>>
I guess the "white stripe" is an eye test. I don't see one, so I guess I fail.

 What I
do see is the standard closely-spaced red & white pinstripes on tank and rear cowl. (Pixelation of digital photos plays tricks sometimes.)
What interests
me, dav, is the decal(?) on the side of the rear fender. ("Mudguard" in your version of English? I like yours better, because it's more accurate as to functionality.)  If the decal concerns specifications and conformity with governmental regulations, we have something similar—but it's displayed on the top of the fender, hidden by the seat.
Gorgeous bike!! It's what mine might have been when it came out of the showroom.