I am a watchmaker and a customer has given me the below watch to service. They also asked me of a rough value for their insurance company, but this really isn't my area at all, I just repair watches and don't resale them.
The hallmark is a London Import for 1916, W&D, The engraving is for 1919.
a realistic auction price would be up to £1,500, and a fair secondhand replacement value for insurance purposes of between £2,500-3,000.
I still have mine down at £500 on my spreadsheet, better update my figures...!