Here we have a World War I period Rolex Trench style watch. It dates to 1917 and has a British hallmarked sterling silver case. It has an excellent white enamel dial, with red 12, clear Arabic numerals and the in-set sub-second dial. The Breguet style hands indicate the time. The rear screw back opens, with the Rolex and W&D signing to the inside. The manual wind Rolex signed Aegler movement has been recently serviced. 
 
This is a genuine Rolex watch, not just a Hans Wilsdorf signed piece associated with his sub-brands. Both the case and the movement are signed. The dial is sterile, as was often the case prior to 1926. This is because British retailers did not allow the names of foreign watch manufacturers to appear on the faces of the watches they sold. On the rare occasion there was a brand name, it would be above the sub-dial, not below 12. 
 
The dial is clean and classic. It is formed of enamel and is in excellent original condition. It is a bright white tone with a railroad minute track around the exterior. The Arabic numerals indicate the hours, with a standout red 12. The sub-second dial is inset into the dial, with 10 second Arabic graduations and individual dashes. The hour and minute hands are thermally blued and are of Breguet style. This is a classic layout of the era which is considered and neat.
 
The silver case measures 30mm x 30mm, with a lug-to-lug measurement of 36mm including the wire lugs. This is a petite wristwatch by modern standards but was originally gents. With the watch head on a bund strap of the era, it wears with an increased presence. 
The case is a good early design which was somewhat water resistant, achieved via the use of a screw front and back. The coin edge finish is good and well defined, with a good thread. 
The crown also sits over the stem with seals providing further protection. This very much resembles the Oyster design minus a screw down crown. One of many experimental attempts on such an early watch.
 
With the rear case back unscrewed, on the inside you can see the British hallmarking from London assay office, for Sterling Silver, which dates to 1917. It is signed with the W&D makers mark, with the Rolex name and Swiss signing. 
 
The manual wind movement is an Aegler calibre. It has the Rolex signing to the ratchet wheel which was usual for the period. It is a 15-jewel calibre, which has a frequency of 18,000 BPH. It is keeping time to within +2 minutes a day, having had a recent service.
 
Early Rolex history:
Hans Wilsdorf began his business in London in 1905 as an importer of Swiss manufactured watches, which he then wholesaled to British retailers. 
With the law change of June 1st 1907, imported gold and silver watches were required to be assayed and hallmarked in a British assay office. This led to Wilsdorfs W&D mark, registered first with London assay office.
He offered a various watches under his import business, but Rolex was the standout. The name Rolex first came about in 1908. He chose this as it was a short, yet significant word, easy to memorise. It has a pleasant sound and its pronunciation remains the same regardless of European language. He registered the brand name in La Chaux-de-Fonds on the 2nd July 1908.
 
The nature of Wilsdorfs imports under the W&D stamp, lead people to claim that watches with a W&D stamp are Rolex. This is not the case. Rolex was a differentiated brand that Wilsdorf reserved for his best watches. 
 
The waters are further muddied due to Wilsdorfs creation of sub brands such as Tudor, Unicron, Marconi and RolCo for other price points. These were still produced under the Rolex Watch Company as he seemed happy for people to feel they were getting a Rolex watch at a lower price. However, he realised this was a poor business plan as it took sales away from the premium Rolex brand. It also diluted the effects of marketing efforts that pushed the importance of a Rolex watch. 
 
Thank you to David Boettcher for the above information which can be found on his website: https://www.vintagewatchstraps.com/myrolexpage.php
 
Please see the images as these compliment and aid the description provided below.
A further condition report is below.
 
Dial: 
The dial is formed of enamel and is in very good original condition. There are no fractures, cracks, chips or hairline marks. It is very well preserved. The railroad track is clear, with the black arabic numerals and red 12. The inset sub-second dial is good and original.
 
Hands: 
The hands are of Breguet style and are original. They are thermally blued, but the finish has darkened with age. The sub-second hand is a later replacement. 
 
Glass: 
The glass is original and is in good condition with no obvious marking.
 
Crown: 
The gold tone crown is a later replacement. It is of suitable design with the onion style design. It is in good condition and functions as it should.
 
Bezel:
The front of the case is formed of Silver and is in good condition with coin edge finish. The coin edge is well defined and the thread is good. The bezel screws on tightly. 
 
Case:
The case is formed of silver. It is a three-piece design with screw front and rear. The central section has the silver wire lugs which are in good condition and un-bent. The case has light surface scratching associated with age. 
 
Caseback:
The silver screw back is in good condition, with defined coin edge finish. It remains unpolished and has light surface scratching associated with age and wear. The thread is good and is screws down tightly. Inside it has perlage finishing with British hallmarking and Rolex signing. 
 
Strap: 
The watch comes on a new genuine leather strap for fixed bar lugs. It is non-Rolex.
 
Movement: 
The movement is a Rolex signed Aegler calibre. It is manual wind, with a jewel count of 15 and a frequency of 18,000 BPH. 
 
The movement has been recently serviced. It’s keeping time to within +200 seconds a day, with an amplitude of 200 degrees.
 
Case dimensions:
Case width: 30mm
Case width with crown: 32.5mm 
Case length: 30mm 
Case length lug to lug: 36mm
Case Depth: 9.75mm
Lug width: 10mm