The date is 1949 as the letter has no serifs and the maker is Cohen & Charles as I do not believe that Collins & Cook would still have been in business then (their Birmingham mark was registered in 1873). I will do a bit of research and post an update later.
Collins & Cook are shown in an 1875 trades directory at 7 Carver Street, Birmingham. In 1909 these premises under the name "Ivy Works" were being used by Hart & Co, "stampers in metal, die sinkers, tool makers and electro plate manufacturers". Collins & Cook may have moved elsewhere but I can find no reference to them.
One further update on Collins & Cook: In the 1879 Post Office Birmingham Directory 6 & 7 Carver Street (the same premises designated as Ivy Works in 1909) is occupied by Joseph Cook, general silversmith. We know that he registered a mark on his own account in June 1878 so it is reasonable to assume that that marked the end of the Collins & Cook partnership. Cook's sole tradership was succeeded in 1888 by Joseph Cook & Son whose registered address when their mark was registered at the Chester Assay Office was 6 & 7 Carver Street.