I actually found a picture of the very engine I saw through the window of the mall, when I was trying to figure out whether it was spelled Mount Clair or Mt. Clare. I stumbled upon this picture and this little blurb about it. I do remember the engine was pretty big...apparently my memory was correct. It was much shinier then, and not so streaky and dirty looking.

"The NS did a cosmetic overhaul on 1604 at the Roanoke Shops before for it was sent (around 1987) to Baltimore to be displayed as the centerpiece of the Mt. Clare Junction shopping center which was adjacent to the B&O Museum. The shopping center was literally built around 1604. In 1989, the failing shopping center decided that 1604 was too big and decided to donate her to the B&O Museum. 1604 was moved from the mall onto B&O Museum property in early 1990 by SW-1 Pere Marquette 11. During the early 1990s, there was a rumor going around that the CSXT was considering starting their own steam excursion program. They reportedly sent some mechanics to check the condition of 1604 to see if it was feasible to restore it to operating condition! Today, the cab has been cosmetically restored and lighting has been placed in the firebox so that it can be viewed."