Photos provided by Ken Skaught, Medallion Estates, digitally processed by Jock Dempsey.
Grid is 1" (25mm) square behind, and 1/2" (13mm) lines below. No dimensions provided.

I had never heard the term "trench art" or of Canadian POW camps in World War I until I started researching this little wood anvil.

The mystery starts with the label taped on the bottom of the anvil,
"P.O.W. MADE WWII - CAMP AMHERST NJ"
The problem is . . there was no P.O.W. camp in a place called "Amherst, NJ". Nor is their a place called Amherst in New Jersey. It did not make sense. So I used an on-line translator to translate the German "Kriegsgefangenen lager". It is "POW camp". So the original maker was definitely in a POW camp in, near or named Amherst. More research. . .

It turned out there was for a brief time a concentration camp in Amherst, Nova Scotia. The only reason there is any mention of it in any accessible literature is that the famous Russian revolutionary Leon Trotsky was arrested and held there for some time in 1917. Trotsky's writing on the subject is very enlightening on the subject of our anvil.

TROTSKY IN AMHERST
by Silver Donald Cameron

. . .Nor did the camp itself impress him: "The Amherst concentration camp," he notes in his autobiography,

" was located in an old and very dilapidated iron-foundry that had been confiscated from its German owner. The sleeping bunks were arranged in three tiers, two deep, on each side of the hall. About eight hundred of us lived in these conditions. The air in this improvised dormitory at night can be imagined. Men hopelessly clogged the passages, elbowed their way through, lay down or got up, played cards or chess. Many of them practised crafts, some with extraordinary skill. I still have, stored in Moscow, some things made by Amherst prisoners. And yet, in spite of the heroic efforts of the prisoners to keep themselves physically and morally fit, five of them had gone insane. We had to eat and sleep in the same room with these madmen. "

At the time of Trotsky's arrival, the former buildings of the Canadian Car and Foundry Company Contained 851 German prisoners of war. Of these, said Trotsky, about 500 were captured sailors and another 200 were "workers caught by the war in Canada," while 100 or so were German officers and "civilian prisoners of the bourgeois class."

The camp operated from 17 April 1915 to 27 September 1919 in the "Malleable Iron Works".

In a Canadian maritime museum there is a model submarine with a similar plaque as above attributing it to the POW camp. I also found this description on-line:

. . . a ship in a bottle made by a German prisoner of war in Amherst, Nova Scotia, 1919. It is a three masted schooner with the German flag and has a background of tiny wooden houses, trees and lighthouse embedded in some type of claylike substance on the inside of the bottle. It is inscribed with the name of the prisoner, place, date and the name of the person who it was made for on a little plaque inside the bottle.

So, obviously someone cataloging the anvil misread WWI and NJ. But the mystery is solved and we learned a little history from it.