William Evans was the 'front of house' manager for the illustrious names he worked for before setting up in his own right. He was not personally a gunmaker nor a gunsmith but no doubt he had a workshop full of them and access to the best outworkers that London could provide.
His guns are usually highly engraved and very well finished but they were generally bought in from Webley, Scott and later Webley & Scott. A majority feature the Webley Screw Grip top rib extension 3rd bite.
He had a similar business model to J Blanch & Son at this time: buy in the best that Birmingham can supply, badge it with a London name & address and reap the considerable mark-up that results.
These facts do not denigrate the Evans name, simply show what a good businessman he was.