6= 1956
2039= 4 door sport sedan also called 4 door hardtop
D= Laurentian
8= 265 V8 engine
24016= sequence number of all 1956 Pontiacs made.
On the data plate there will be Body no. Trim no. and Engine no. and BSO nos which are the options installed at the factory. The car being a first year 4 door hardtop for Canadian Pontiacs is very rare. You can look for the third pedal and linkages to see if it was a standard trans. Good luck with your project.
