Had anyone ever come across the hallmark L+G in an Oval on a watch case. This one is on a French imported trench watch presumeably WW1. Thanks

It has the look of a manufacturer's marking but I do not know which one - there were so many.

Is there a reason you are calling the watch a trench watch? If you could please add some photos of the front, the back, and the movement that might help. Many people use the term 'trench watch' rather liberally these days. Most all of the ones out there are not actually military timepieces but rather civilian watches that were made in the style to appeal to people's tastes of the day. Of course some were purchased privately by some soldiers and worn during the war, but these are not actual military watches.