what is the car

[DARRAN]

what is the car in the foreground on the back of a u.s $10 bill

[kempie]

The design on the back is the Treasury building. The 1928 edition featured a car parked outside of the Treasury Department building. Contrary to popular belief, it is not a Model-T Ford, rather it is a composite of multiple cars of that era.

http://www.answers.com/topic/u-s-ten-dollar-bill

[kev100]

According to this it's a Hupmobile

Left side third paragraph down.

http://www.geocities.com/dkd62_2000/FunFacts.html

[Marsh]

Perhaps not:-

Is the car on the US $10.00 a Hupmobile?
No, the periodic rumor that the car on the old-style US $10 bill is a Hupmobile has been strongly denied by the US Mint and the Bureau of Engraving. The original engraver used a composite of many US cars so as not to favor any one manufacturer.

From http://clubs.hemmings.com/clubsites/hupmobile/faq.htm