Alco Switchers with Horizontal Shutters.
http://www.rr-fallenflags.org/nh/nh0603.jpg
http://yardlimit.railfan.net/archive/bn/010_031.jpg
The NH 0603 has a flattened cab roof to clear catenary wire on electric districts.
It also has an Air Whistle!, normal on NH Switchers of the era.
An Alco Switcher with Vertical Shutters, which was more common.
Can’t tell why they are horizontal - but as we have a set in pieces at the West Coast Heritage Park in Squamish BC - can tell you that maybe they went vertical because of corrosion- which we found had rusted through in the same spot on seven of the slats - we are in the process of repairing both side shutter assemblies on our Also S3 - ex CPR #6503