I was reading a document by John Vigiano (Retired FDNY Captain) entitled Forcible Entry Forcible Entry Reference Guide. Chapter 1, Forcible Entry History.
Apparently in the early years of FDNY, there was a bank robbery. The robbers set a fire to cover their tracks. In the aftermath of the fire, there was tool found that the robbers had used. The tool was about 36″ long, and had a hook on one end and a fork on the other. The tool was dubbed “The Claw Tool”. They figured if it’s good enough to break into banks, it was good enough for the fire service. Many companies copied the tool and it became very popular.
The short-coming of the claw-tool was the fact that because the claw was curved, it make striking the tool a risky proposition.
Because of the short-comings of the claw tool, John Kelly of FDNY ladder company 163 set out to build a tool with a straight impact line. He removed the hook and added an “adz” at a 90 degree from the shaft.
Here is a pic of the Kelly tool
The claw tool was very popular and had become the primary forcible entry tool. It was paired with the Kelly tool and together they could force nearly any door.
Over time they became known as “The Irons” and the firefighter that carried them became known as “The Irons Man” (not to be confused with Tony Stark)
Because these tools were unwieldy, Chief Halligan set out to improve them. His tool was lighter (at 8.25 lbs), a swept adz, and an added 90 degree pike. The Halligan incorporated all of the best features of the Claw tool and Kelly tool and had none of the detractors.