Well, there does not appear to be a recognizable trademark. From your confirmation of the proof marks, it was proofed between 1853 and 1877.
Geno is of course correct. This was meant for the English or American market.
Those hammers are very unique! I am sure that they were not a common item, even then. As others have stated, they are the key to the maker. I tried EJ Blackely, but it appears their site has moved.
You might try Alan Trigger. He owns one of the better Belgium sites for proof marks. Concentrate on the hammers with him.
http://www.littlegun.be/mise%20a%20jour/a%20fiche%20mail.htmPete