I'm not entirely sure if they are London, although the Lion Passant does not look provincial.
They are the usual three piece construction, but a curious feature is that the Assay Lion is punched below the join on one side , and the makers mark above the join on the other . Normally both are punched ON the join, on opposite side s. Makes photography of the makers mark very difficult as my wife has an objection to me straightening the bow to get at it !
The marriage inscription being inside is unusual also. No sign of any other owners initials on the bow
Note that this is two separate photos of the same mark