That is an B&O M-15H and I have attached the photo I presume was in the link that I cannot get to work. The roof is not documented, but the end, as mentioned, was a Tatum XLT end with differences from the Indestructible End. Tatum was the Chief Engineer for the B&O and patented his ideas and the B&O used them. You are probably are all familiar with his brake slack adjuster that appears on the side of B&O M-53 boxcars (and others) as a steel plate with a ratcheting mechanism.
Bruce D. Griffin