Dump find – Roofer’s Tool?

I found this at the town dump last week, I'm speculating that it's a roofer's tool for bending flanges on to sheets of copper.  It's about 4 feet long, the hinges are brass and there is a steel blade edge on both side of the central slot.  It is clearly for bender rather than cutting.

Let me know if you recognize what this tool is for!