Your model is 750TR and chassis number 415427.
B28L/17069 will be the build code and will probably include the original colour.
It was built in April 1971 (4.71).
51VD/1508ZG/2465? is the VIN (a unique Vehicle Identification Number) which will define where it was built (and by whom) and, when.
http://en.wikipedia.org/wiki/Vehicle...nts_of_the_VIN
Maybe
Audiman can be more specific?
Edited to add that your vehicle was built
before the VIN was standardised, and, from 1954 to 1981, there was no accepted standard for these numbers, so different manufacturers used different formats, so the above Wiki article doesn't apply!