The Baltimore & Ohio and the Philadelphia & Reading (reorganized as the Reading Company in 1923) had a close relationship but they were not combined. There was talk of merger during the bleak times of the late 1960's and early 1970's but Conrail was formed instead (April 1, 1976).
Cabs of Reading steamers had a separate window and seat for the head brakeman behind the fireman's seat and window, like B&O cabs.
The most remarkable result of the close relationship of the B&O and the Reading was the construction of 20 (then 30) T-1 4-8-4's (1945-1947) and 10 G-3 4-6-2's (1948) in the Reading Shops along North Sixth Street.
On January 1, 1942, A. K. Galloway resigned as Superintendent of Motive Power and Rolling Equipment (MP&RE) on the Reading. E. P. Gangwere replaced him. Mr. Gangwere orgaized a comparison of EMD FT's, 2-10-4's, and high-speed 2-6-6-2's. The B&O had purchased 16 Mallets from the Seaboard Air Line in 1922 and built an experimental 2-6-6-2 (Class KK-2) in 1930. Mr. Gangwere advised the Reading to make do with locomotives on the roster and dieselize as quickly as possible after World War II.
But in 1944, Revelle W. Brown, a former B&O engineer, succeeded succeeded Edward W. Sheer as President of the Reading. His fondness for steamers is well documented. He obtained detailed information about Lehigh Valley 4-8-4's and passed it to Mr. Gangwere. Meetings in President Brown's office on August 1 and 4, 1944, led to the construction of T-1 4-8-4's and G-3 4-6-2's. Nods to Lehigh Valley 4-8-4's ("Wyomings") were the class letter ("T") and the numbers (5100 became 2100, which fit nicely after the numbers of gigantic I10sa 2-8-0's [2020-2049] that provided boilers for the T-1's).