Here we have the best kept example of a trench watch we have seen in many years of dealing in vintage watches. 
Dating to 1924, this is an outstanding Longines trench watch, retailed by JW Benson of London. It has the 35mm silver case with the screw front and rear. It has the patented swivel lugs which help it sit comfortably on the wrist. It has the eye-catching onion style crown to the right-hand side. The white enamel dial is bright, with the railroad minute track and the Italic font of Arabic numerals. They have the original Radium luminous paint which has aged. There is the in-set sub-second track at 6 O’clock. The hands are of Cathedral style with the thermally blued finish and luminous in-fill. It has hallmarking from London assay office to the inside and the manual wind Longines calibre 13.34 movement. 
It comes on its original leather strap with the original 1924 hallmarked buckle. It is in exceptional original condition for its 100 years of age. It comes with its original box.
 
The dial is white enamel and is in outstanding condition. It is a crisp white tone, with a railroad minute track around the exterior. The hour markers are large, stylised, Arabic numerals. They are in-filled with the original Radium luminous paint which is in excellent condition, with a lovely pumpkin tone and puffy texture. It has the in-set sub-second dial at 6 O’clock. It has single second, 5 second and Arabic 10 second graduations clearly marked. The dial is signed below 12 “JW Benson London” with Swiss Made to the base of the dial. The cathedral style hour hands are original and are a bright thermally blued tone, with the aged radium luminous paint intact. The sub-second hand is original with oval counterbalance.
 
The Silver case measures 35mm x 35mm, with a lug-to-lug measurement of a whopping 45mm. Early Longines trench watches like this are known for their distinctive swinging lugs, at 12mm in width. The design was registered to Longines in 1907. A tube soldered to the watch case carries a bar, that the lugs (a loop of wire with widened ends), are attached to. This makes the watch a comfortable fit to the wrist, with the lugs angling down with the strap.
The bezel screws on, with the sharp coin edge finish to the outside. To the right is the original champagne tone onion style crown. To the rear, there is a screw on back with coin edge finish, matching the bezel and providing a symmetrical case design. Inside it is signed with British hallmarking from London assay office, dating to 1924. The serial number 4,171,732 is engraved to the inside. It has the ‘AB’ makers mark for Arthur Baume, UK importer of Longines. The case has an even tarnishing across all elements of the silver and has not been polished.
 
Inside is the Longines calibre 13.34, which was introduced in 1910. It carries the marking for Baume & Co who were the importer for Longines. This is the 15 jewel variation which is in very good condition, keeping good time to within +40 seconds a day, with a strong amplitude.
 
The watch is presented on its original tan colour strap which is in good condition. It has the original Silver buckle which is also hallmarked for 1924. 
 
Overall, this is an exceptional, collectors grade original example, with a high-quality design, case and movement. 
 
*Credit to David Boettcher and his Vintage Watch Straps website for the above information on the Longines lug patent*
 
Full condition report below. Please see the images as these compliment and aid the description provided below.
 
Dial:
The dial is enamel and is original. It is in excellent condition with no hairlines, fractures or chips. This is as good as dials from this era can be. The signing is very good and clear. The luminous paint is original and very good.
 
Hands:
The hands are original and are of cathedral style. They are thermally blued and have the original radium luminous paint intact.
 
Glass:
The glass is original with the bevelled edge and is in good original condition. It has some slight dints to the edges.
 
Crown:
The crown is original with coin edge finish and is in very good antique condition. 
 
Case:
The case is formed of silver and has a screw on front. The screw on front has a coin edge finish and is in very good antique condition with good definition. It screws on tightly and the thread is good. The hinged lugs are very good and original with no repairs. The hallmarking to the side of the case is crisp.
 
Caseback:
The screw back is in very good antique condition. It has light surface scratching and has polished with wear against the wrist. It has a coin edge finish which is very good and well defined. It screws on tightly and the thread is good.
 
Strap:
The watch comes on its original tan colour strap which is in very good antique condition. It will fit any wrist size and is soft and strong. It has the original Silver buckle which has not been polished and has the tarnishing intact.
 
Movement:
The movement is a Longines cal 13.34. It has a jewel count of 15 and has a frequency of 18,000 BPH.
 
The movement is running well, but the service history in unknown. It’s keeping time to +40 seconds a day, with an amplitude of 275 degrees and a beat error of 1.6m/s.
 
Case dimensions:
Case width: 35mm
Case width with crown: 38mm 
Case length: 35mm 
Case length lug to lug: 45mm
Case Depth: 7.25mm
Lug width: 17mm