In June 1942 some engines had their pilot beam mounted marker lights move to the smokebox using oblong multi-lens marker lights. Not sure if any of the Lionel models have this configuration.
PRR stopped using classification lights in 1940, so if the engine has both classification lights on the smoke box and marker lights on the pilot beam, that configuration would put it between 1922 to 1940.
You can thank Ed Rappe for the data (hope I got it right).
