I found these three slides of the lake in a collection of commericial slides. Some indicate that they were published by Don Sieburg & Co, New London NH.
My Grandmother worked at Technicolor in the 60's and I believe she took the slides as rejects. There are dozens of different scenes from around North America, but the labels are double printed or just wrong.
I'm willing to donate a set of the actual Winni slides to any historic entity that wants them and will preserve them.