D51-498 was this loco special?

[Super]

Really? So the 498 designates only one train when it was built? Strange, because looking at these pictures there looks to be different 498's and the photos don't all look old. Learn something new everyday as I didn't know that about the numbers and just assumed it denoted a certain series of D51's
https://images.search.yahoo.com/yhs/sear...mp=yhs-001