Anyone know how close to scale (1:48) this engine is? I always thought the tender was too big.
Elmer Steurernagel in PRRT&HS’s The Keystone Vol 35, Number 1, Spring 2002, had a lot on PRR classification lights. Here are two data points related to the OP.
1929 – shops ordered to remove classification lights from locomotives assigned to yard and freight service (except M1/M1a's and other freight locomotives regularly assigned to passenger service
1940 - PRR ceases to use the train classification rule (extra, second section following) - shops ordered to remove classification light fixtures from locomotive smokeboxes.
Not sure about other roads that used the B6.