Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 135,384 pages of information and 216,989 images on early companies, their products and the people who designed and built them.
of Watford, maker of self-toning papers, bromide papers and plates and colour process.
Presumably previously Paget Dry Plate Co
1887-1895 Records of the Paget Prize Plate Co Ltd of Watford, photographic materials manufacturers 
1914 Exhibited 'Bromide Enlargements from colour negatives' at the Royal Photographic Society 
1921 Amalgamated Photographic Manufacturers Ltd was formed bringing together seven British companies:
1929 APeM subsequently became part of Ilford