The only Newhouse trap wrench I know of is the one below. trap collectors have been running wanted ads for years trying to obtain one. I have never seen an example in all the wrenches I have handled.
Picture is from
http://trapanswers.blogspot.com/ with the following caption:
"A Newhouse wolf trap combination tool, used as a hammer, wrench, and spring compressor; it's also used for making adjustments to the trap. Another rare piece, if you happen to have one, they are worth over $1000."
Also found this description in a 1908 Hunter-Trader-Trapper magazine"
"Newhouse Wolf Trap Drag and Wrench These drags are very convenient to fasten to traps They will either securely hold the animal or make a trail that is easily followed Drag made of wrought iron furnished with strong S Hook to fasten to trap chain Price 25 cents each
Wrench is of malleable iron With a pair a trapper can set a No 4 or 4 Newhouse wolf trap very easily Has small slot in end for bending the dog The flat surface near one end will serve as a hammer Has also a long slot in middle for slinging on carrying strap Price 25 cents per pair One Drag sent postpaid for One new subscriber One pair Wrenches sent postpaid for One new subscriber Newhouse Fox Trap Drag"
The wrench on ebay can be found marked "M58" or "N9", as far as I know they are both orphans. I can't imagine how a small (5-3/4" long) wrench like this would be used on a wolf trap but I could be wrong.
Rustcollector: I have several of each so if you sell you for $25 each I will sell you ten more for $5 each. I also have one unmarked example.