Nice.
Is it real? Looks to be. The "thick" lettering makes it post 1953.
RICO, I don't think Santa Fe bridges used this type of sign. SD45T-2's sign is more for stations and other buildings. The bridges I know use black and white heralds and they are painted on not placards. There is a unique bridge in Williams, AZ with a blue herald, but it is painted on and not a placard like SD45T-2's sign. There used to be a blue and white herald (painted) on a bridge over the 91 freeway in California, but this has mostly weathered off...could be completely gone by now.
Collecting Santa Fe memorabilia can be addicting. My dad and I have been collecting Santa Fe items for many years. Our prize pieces include a station clock and lounge car smoke stand.