Reason behind Boeing's "720"

From: (BBost0325)
Organization: America Online, Inc. (1-800-827-6364)
Date:         10 Jul 95 03:18:15 
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To all who are wondering about why Boeing's 720 doesn't follow the
standard 7x7 desgination, here's the answer:  When Boeing proposed a
lighter, shorter 707-120, they naturally called it a 707-020 (similar to
what Airbus is doing with the A319, A320 and A321 series).  When United
came around to choosing this aircraft to complement their DC-8 aircraft,
they complained that the "707-020" designation made it sound less advanced
that other 707s. So Boeing changed the designation to 720.  Yes, it's all
marketing.  The same thing happened to the DC-10.  The DC-10-20 was
changed to a DC-10-40 on request of Northwest Orient.  (This information
was taken from AIRLINERS magazine, which I HIGHLY recommend to all
aviation buffs.)