Question for any PRR experts out there....in my research on the Pennsy, I've noticed that any engines operating in its Midwest territories looked significantly different than typical PRR engines we're used to seeing....they had a front-mounted headlight, sometimes different tenders, and seemed to have powered bell-ringers before engines on the east had them. At some point in history, this stopped and Pennsy modified even the Lines West engines with the typical keystone/oval number plate, with top-mounted headlight.

Does anyone know exactly WHEN this occured? Was there a specific reason, other than the desire to standardize it's entire fleet?

It seems to me, that going by picture dates, it may have occured between 1923 - 1930, but I'm not sure.

(Personally, I rather liked the Lines West look.)