there is a Walton's audio chain in Douglas - I don't know what connection if any this has with the Edwardian photographer (he must be post 1894 as not in the directory of that year) - however 2 WW's and the collapse of tourist trade has probably meant that any archive or records are long gone - I know the Manx Museum has many Marshall Wane slides but I don't think they have any index to them so don't know who is on them !

You best bet on dating is generally the clothes worn