Need help identifying this very unique key

[maintainer56]

I owned and operated my own locksmith shop for more than 25 years and have been a lock collector longer than that. I recently purchased a large lock collection which included this key. The major details and notes about the surface can be seen in the photo. This is a brass hollow post key. Believe it or not, The tip has a metal tubular insert which has ten rows of dimple cuts running the full length of the inside surface! Never seen anything like it. As you can see from the handwritten notes in the photo, ADT with an arrow pointing to the bow is stamped on the blade next to the removable steel insert on the blade. Like to know what it was used for and the value.