checking the height with the tell tales (only the 2nd time I've ever seen a photo of these in use)

I just discovered this method a week or so ago  https://justacarguy.blogspot.com/2023/02/what-do-phrases-all-bells-and-whistles.html  but this photo is far better resolution and shows a train using the tell tales

https://www.flickr.com/photos/boston_public_library/6008641837/in/album-72157627356059350/