The painting is lacking in artistic skill (in fact quite amateur in nature) and therefore could have been completed by anybody within any timeframe. I am assuming it to be watercolour and if the paper is aged, there is a possibility of it being a wartime painting, however this would be very difficult to prove. I am not aware of any artist signing of 'W.A.G.' in such a manner, and any professional artist will ensure he/she receives appropriate accreditation for their work with a readable signature. If framed, any notes on the reverse of the paper may shed a light on its provenance. In summary; it is only worth what you would be prepared to pay for it if you wished to add it to your own collection rather than a potential investment aimed at future profit.