Thanks once again for the speedy response.
I've been examining these in great detail for months. Apart from what's been mentioned here, there are variations in the detailing on the harp box, the scrolling on the top of that box, where the scroll ends attach to that box (relative to the detailing upon it), also upon the crown. Wear and tear can change things I know, but these differences are not as a result of years of use.
Maybe I shouldn't get too hung up on some minor details, but a fine looking example would bring the search to a close 🙂