RGS and C&S Slide Mystery Meat

Out at the big Springfield model railroad show this winter, I picked up a whole metal slide box full of narrow gauge Colorado slides. It was one of a pile of items that had been donated to some museum and they were selling off to raise funds. They didn't know the provenance of it, and I didn't have time to stand there and sort through slides, but I figured the price was worth a shot at some good stuff and went to help some railroad museum.

Over the last few weeks I've finally gotten around to going through it. A lot of it is Chione sets and other stuff that's clearly copy slides, but then there's a selection of other stuff. Some clearly copies, some I think are originals. Quite a few I've been able to pin down so as to add locations, dates, photographer info, etc. to the scans. Others remain slide mystery meat, so I thought I'd post a few here and let you guys have a crack.

1 - The first one I think is from a trip over the RGS by motor #3 in June of 1951 (based on notes on the slide mount and nearby photos) and may be an original. It's an RGS tank somewhere, but doesn't line up with any I recognize.

2 - An unknown C&S engine leading in what I think is Waterton Canyon, possibly a westbound right about here:
[maps.app.goo.gl]

3 - What looks to be a special with C&S 61 & 76 on the front. Judging by the poles, this is somewhere on the old South Park line. My guess would be heading south out of Denver along the South Platte before turning into the mountains.

If anybody recognizes these and can put locations, dates, and/or photographer names with them, I'd appreciate it.