Not homemade, specialty made.
I picked up a pair at a yard sale about two years ago. The owner didn't know anything about them either.
The handle has the Peterson/Dewitt stamp.
But the top jaw is stamped :
GIRARD
Steel & Equipment Co.
St. Paul, Minn.
No model number. I never learned anything substantial about the company, or about the pliers.
I'm not sure if Irwin still does it, but the original Peterson Company used to sell parts wholesale to licensed companies so they could make specialty tools for specific tasks.
The consensus at the time I found mine was, as mentioned above, that they may have been made to match a raingutter profile.