You bet old car price guides exist!   There's a magazine called, amazingly
enough, "Old Car Price Guide" that is issued 6 times per year.  There's
also an encyclopedia of old cars, 1895-1942.  Actually the encyclopedia
comes in 2 volumes, with the second volume covering the more modern cars
from 1946 and on.  These publications attempt to list the value of all
the cars.  They list the cars in either 5 or six categories, with number
1 condition being absolutely pristine showroom condition, and number
5 or 6 being a basket case, i.e., all there, but apart, not running,
not serviceable, and requiring total restoration.  Several problems
are presented.  For starters, there are over 5000 makes of cars, and
they're not all listed.  The prices listed are based on known sales or
auction prices, and if a particular car hasn't been reported sold for
awhile, the listed price will be old.  Further, when a car is sold, an
estimate has to be made regarding its condition, and the estimates for
other models in better or worse condition have to be made.  Finally, the
location of the car has something to do with the demand, and hence, the
value of the vehicle.  Bottom line -- the values shown are "guides", and
should not be used as anything else.  In my experience, the prices that
cars bring when sold to fellow club members represent the fairest
estimate of their real value.  I'll bet that's true in the mechanical
music hobby too.

Ray Fairfield