Gas
You are right, it would be very hard for some of the so called "Trench Art" to have been made in the field.
The BB ring was made in a prison camp, even harder. Looks too good for that.
I'm into US WW11 fighting knives. the Trench made ones are very popular now, and there are millions of them for sale.
There must have been a lot of trench machine shops in the field during that time.
It was World War Two, how did these guys have soo much time on there hands to make knives?/
It's part of the intrigue, we will really never know about some things.
