model 511 - 1951 Kaiser Special
body 1 - four door
paint 370 - Mariner gray
trim 1130 - Explorer gray Richmond
dr 1 - Delivery Region U.S.
tr 2 - three speed transmission
ag1 - Accessory Group 1 (directional signals, oil bath air cleaner)
131 1373 - schedule and item number refer to the car's position on the assembly line
The info to decode these numbers is found in the book 'The Last Onslaught on Detroit'