Bill, I tried your email address link. While partial and in blue, it does not seem to go back through Yahoo as it once did. Instead it opened Outlook Express on my machine and is incomplete.
Photos seem to suggest that all B&O C-16 class wagon top express
cars had slab-sided doors, even the last 25 that were in express service until 1958 with several
wearing rare, blue paint jobs.
At that time all the wagon top express cars were returned
to freight service as M-53 class cars, with their former freight numbers. When put back into
freight service they also got Youngstown door upgrades.