Usually, a vehicle with a September build date is considered the next years model, in this case, a '46. But some state registered them by the year sold, rather than the model year, which has lead to some confusion, especially when there were definite technical or cosmetic differences between years.
Another issue, especially with the Wartime production, is during the '42-'45 period, GM listed them as '42 models, rather than the actual production year (this information varies by source).
They way I see it, it has a '45 build date, a '45 title, then it's a '45 in my book.
