Distingushing features in pictures:

• Four Stacks
• No plow early on, plow added along with a metal plate attached to the handrails, looks like plow might be temporaly mounted for the winter only
• Black cab sunshades added in later years
• MU added in '64, after that both #100 & #101 were usually seen togeather
• Yellow stripes on front stop for radiator
• Yellow side handrails
• Also had lengthwise grab on hood
• Black front & rear square cornered railing
• Yellow Frame rail
• Nathan M3 (3 Chime) horn? mounted cab roof front (hood) side
• Silver trucks, although some shots they appear to be dark, most likely just really dirty
• Class lights? Marker lamps? similar to those on a caboose mounted on front hood corners
• Steam style bell moved a few times, for a while was mounted with a plate under it, sticking over the edge, later centered
• Radiator covers seem to be seasonal, the continuting stipe one looks like it was made for the S12 although they switched
• Two had three openings, and one with two openings, one of the three opening covers had continuing stripes (picture warning)
• Hood side numberboards have unit number.
• Rotary becon mounted directly to the light box on hood front.

Extra info:
Baldwin, built 4/1947