This has been debated before. I can't recall the outcome.
My answer is that the journal box lids were not uniformily painted silver until the fifties.
Striping on the running boards and below the cab was done as a safety requirement. Striping under the tender tank and journal box lids was pretty common by the late fifties.
In the 60's, of course, it was "standard". That's where so many great pictures we have come from. I like it.
Mike