Is there a way to visually distinguish the difference between a 747-100 and -200 (with 3 windows a side on the upper deck?)

I think I've logged flights on all the major variants except the -8i and -200SUD.

SR (JL)
-200 (SQ, CX, BA, QF, NW, CP, PR, PA, PK, AR) - some may have been -100s (it'd be BA or PA)
SP (PA)
-300 (CX and QF)
-400 (UA, KL, NW, CX, QF, BA, CP)
-400ER (possibly, QF)
-400D (NH)