The first thing you need to do is read the sticky in this forum "How to Sell Ukuleles in the Marketplace: READ BEFORE POSTING" as no one will look at your sale seriously on here until you conform to the accepted rules.
I have just googled this uke and its maker and I can find his website and some other links. I cannot find any reviews of other Davidson ukes so have nothing really to go on regarding what sort of sound it might make, potential issues, good and bad points etc. Most other ukes have easily available reviews, I know it's not your fault for this uke! Unless a potential buyer knows someone who has played one then they can get no help on what to expect from this instrument.
I would also include a photo of the label as there is nothing else to positively identify this as a Davidson. Do you have any other documentation e.g. receipt, invoice? For example when was it made? Is it a standard model? Does it have any custom features?
Also why are you selling it? I would want to know how come you have never played it, is there something wrong with it?
Does the price include shipping?
Also one of those links said you could get a new Davidson uke for £750. In my opinion £650 is too high for a secondhand one based on the retail price but obviously you are entitled to set your own price. If you are willing to consider offers then add that to your description. IMHO the person who made it is not necessarily detached enough to make an objective appraisal.
Hope this helps and good luck with your sale.
