I have been offered this trench watch in part exchange for one of my pocket watches but I know nothing about trench watches. So a little advice would be appreciated from the more knowledgeable. The case is Sterling silver and the dial has the logo I.T.A. & Co. The watch is in good working order. Is it worth the £150 the owner is asking?

Does the movement have a maker's name?

So called trench watches were rarely issued by militaries - for the most part they were commercially sold by jewelry stores not only to soldiers but also to the general public who wanted to be fashionable during that era. Ones issued by militaries are normally marked by those militaries both to ensure inventory control and make sure soldiers did not sell them. The metal grills some of these wrist watches sported, such as the one you are seeing were to protect the crystal, but they do not say whether or not a particular watch was officially issued by a military, or whether the watch was privately purchased and used by a soldier, or whether it was bought by a civilian and never came near the war. I still see these grills offered sometimes for adding to old watches to make them appear to be of the era. These are like tank watches, most so called tank watches never came near a tank crew member or even a military anywhere. Or so called pilot's watches where some people like to imagine that an old wrist watch with widely spaced lugs must have been used by a pilot with an extra long strap to go around the outside of a flying coat.

I cannot say whether this particular wrist watch is worth the asking price - mostly that would depend on the maker and quality of the movement inside and whether you like it. I would not attach any additional value to it being something that might have been a private purchase by a soldier. After all soldiers also made private purchases of rabbits foots, religious medallions, and the like that normally do not add any value to those objects either unless they have an interesting inscription engraved on them or such.

Peter: Interesting looking watch. Is the shield (grill) an original part of this case or is it just added on and held in place with the band, Some of them are the actual outer bezel and have an inner bezel which holds the glass. Is this a hinged case. Any possibility of showing the movement. Am a little suspicious the crown is not original.

I'm as skeptical as the other responders.

The dial is significantly aged, the hands are new.

This watch has been gone through. As a rule, I prefer to leave everything original... or, make everything new... I tend to shy away from one that has an odd mix of old and new. Either restore it, or leave it alone.

I've told the owner that I will not be doing a deal on the watch.
Thanks everyone for the advice, I knew I could rely on you.