Most everyone loves a good mystery now and then. So here's the evidence: For a number of years, I've had the following stereoview. The photographer's business address is printed on the front. Nothing unusual there. And in pencil, on the back, is the same town indicated: Milford MA. Just recently I went over the reverse side with a fine tooth comb. Ok - it was actually a magnifying device. Barely visible were the words "Indian Fort". And that was mostly due to a fine indentation in the cardboard. Not much pencil to speak of.
So, although the business address is a nice starting point, it by no means indicates exactly what town where this rocky formation may exist.