B28 is indeed October 28th. The trim tag was applied after body painting. The rest of the trim items would then be applied and the car would be rolled to the final assembly area to be mated to its undercarriage, usually about a day and a half to two days later. The body number was basically a production tracking device. Your car had the 1402nd convertible body that came off the St. Louis asembly line for model year 66. Your car's VIN should indicate that your vette was "born" somewhere between 10/29/65 and 11/2/65. The 29th was a Friday that year, no work during the week-ends. I'm assuming you know what the rest of the numbers on your trim tag mean.