Volrider,
I expect you've seen it, but there's a picture of one on page 46 of the May/June 1999 (no 57) of 'Airliners'. It's G-AZFB, ex Northwest.The mag features a major article on the 720. The font looks like a variant of arial bold italic, only a bit squashed up, to me...
Cheers,
TheOddOne