Photos provided by Andy Mason, UK, digitally processed and grouped by Jock Dempsey.
The tunnel stake is similar to the blow horn stake but without the long slender horn opposite the broad partial cone. Why they call these a “tunnel” stake is unknown. However, it is surprisingly similar sounding to “funnel” which is a shape that could be formed on this tool. American tunnel stakes are supported more toward the center of the tool.

This is an open die or hand forged tool, the head forge welded to the shank.