Hey! I never noticed that the two lettering styles were the same until now!
Many of the other forum members have touched on the fact that the Reading and the Western Maryland were members of the "Alphabet Route." Despite being a coalition of railroads that were intended to compete with the B&O, The Reading, CNJ, and Western Maryland all fell under the B&O flag eventually. The stopped using the same lettering styles after the Readings bankruptcy, and after B&O(Controlled and influenced by the C&O) divested itself of the Reading. Basically, to understand how they were connected, just remember that the Reading and the Western Maryland had alot in common in terms of equipment and standards, while the B&O and CNJ were fraternal twins. Ironically, just before Conrail was created, Chessie tried to pry the Reading away from them, without getting it's debt. Pretty sneaky, don't ya' think?
To put a long story short, the B&O Controlled the Reading through the Western Maryland-RDG partnership, aka. the "alphabet route," therefore they shared a degree of commonality.