I have always noticed the notches in some grab irons on passenger car roofs but really never gave them much thought until necessity required it. I was up on the roof a lot this week working on our diner and was glad to have them.
Now that you mentioned it - I looked back at some old photos in books about B&O diesel locomotives from Gen 0 through CSX. Noticed the hand holds near the top of the nose of both the E and F units had similar hand holds to allow for ladders.