A colleague has a piece of trench art: about six inches of an empty artillery cartridge, with the base, that had been intricately carved. The seller said it was a World War I specimen. But she measured the diameter of the cartridge, and it is 88 mm. Does this mean it was likely a shell for a WW II German 8.8? Thanks.
The Germans had 88mm shells in WWI, so you can’t say when it was made just based on the size alone.
ETA: Note that trench art wasn’t always made in the trenches. Sometimes it came from POW camps (another place where men often had a lot of free time on their hands and limited materials to work with), and after the war a lot of trench art was mass produced using military surplus once folks found out that there was a demand for it.
Thanks! Did anyone else use an 88 mm shell?
They did? Everything I can find are either 7.7 cm or 10.5 cm guns. The 88 is, AFAIK, a WWII anti-aircraft/antitank gun.
World War I German 88 mm anti-aircraft cannon. Photo taken in August, 1918.
ETA: This gun was modified in the 30’s and evolved into the well-known “acht acht” from WWII.
While poking around the net to see if anyone else had 88mm shells, I discovered that the 88’s in WWI were nicknamed “whiz-bangs”.
from: To Conquer Hell: The Meuse-Argonne, 1918 The Epic Battle That Ended the First World War by Edward G. Lengel
engineer_comp_geek is right “trench art” was rarely produced in a trench where other things took precedence. Most of it was produced well after WW1 as tourist pieces for people touring the battle fields. The fields etc were littered with shell cases and the locals made use of them. Or bored engineers making things to send home, though just how they “found” the raw and much needed materials is a question. Today wandering a local “antiques shop” i found a pair of shell cases that had been spun into baluster shaped vases and that took a lathe at the very least!
You definitely know much more about this than I do, but in IMHO, the uniforms in this picture don’t look German to me. 
OTOH, the soldiers in this picture appear as if they inspecting a foreign (enemy?) weapon. So they aren’t German soldiers after all.
The Wikipedia info says that it’s a photo of a captured German gun, so I wouldn’t expect the uniforms around it at that point to be German. 
Here’s the description for the photograph:
World War I German 88 mm anti-aircraft cannon. Photo taken in August, 1918
I’m also pretty sure that these are Russian/Soviet uniforms (but IMHO, from a later era). However, by that time (summer of 1918), a truce between Russia and Germany had long been signed, there was no fighting. And also, according to Wikipedia, prototype 88s were first produced in 1928. I’d say the caption for the picture is wrong, but again, I’m no expert.
Well, here we go:
Guns captured by Canadians on their way to Gun Park. Battle of Amiens
(I have never seen these Canadian uniforms before).
Thanks everyone for all the thoughts and info.