The Eternal Question:
You've asked it, you know you have. Can a Robbins punch dagger go through the door of a '48 Roadmaster?
   

I don't have a Buick but Elmer Butts fits the vintage, Detroit iron description
The stage is set...
Action shot! And no crap from you martial arts types about my lack of form.
Closeup from the earlier pic. Notice, it's at the moment of impact.
The damage is done. A hole about 3/8" X 1/16"
I lost about 1/32" off the tip. Not perfect but it fared better than Elmer.