"Upon further review", as the sportscasters say, I am sure you are correct and were all along. Over the years, I have seen period photos of at least three different 1946 Cadillac Model 62 sedans claiming to be "the first one off the line" after the war, and have also read an article by a collector who claims to have the actual car. They can't all be the real one - but your photo of the car coming off the assembly line with GM officials and a sign in the window is pretty conclusive. My apologies for having doubted you.