This loco is a 1926 oil burning 4-8-2 "Mountain" type, (4 leading, 8 drivers, 2 trailing) that was made surplus in 1951, donated to the Museum of Transportation (in St. Louis, Missouri) in 1959, and restored to working order in 1988 for it's excursion career. It's new lease on life lasted until 2002 when insurance costs and a failing boiler made the engine enter it's second retirement, while will be probably be forever.
The model you see here has been my dream ever since I was 5 or six years old and rode behind the steamer on one of it's last public trips. (I don't remember much of the trip, but I do remember the sense of awe and respect for the power of steam after seeing the loco pull past us on it's journey back to the museum and into what looks to be permanent retirement.)
The LEGO model of the 1522 is sitting on the front of the real deal.