It appears the display was moved to the Alanson depot in the late 1970s and was removed during the mid to late 1980s.
I determined the locomotive to be Southern Sand & Gravel Co. No. 102 which is now located at the Steaming Tender Restaurant in Palmer, MA (after being moved several times).
Now the only part of the mystery left to be solved is what happened to the bunk car and the caboose?
Photo at Harbor Springs by Hartland Smith
Photo at Alanson from Joe Granger