Unfortunately the BBFC are not as good as they should be I have had several communications from them in the past which have not been totally accurate. I have material from Dracula's Daughter and Son of Frankenstein both from the first release in the U.K. and all have G.F.D. printed on them. As dose my "The man who knew too much" from the 1934 yet most of the history books say J.A.Rank formed G.F.D. in 1936 yet they are credited with films as far back as 1919. As to Frankenstein and Bride, and also on my Invisible man items, it dose have "A Universal Release" printed on them, but I am not sure Universal handled their own releases over here. I am sure it was done via a British Distributor. ( I must get all my books sorted out ).
Early cinema in the U.K. is very muddled, and dose not clear up until the late 30's. RB possibly stands for Rank British, it is also possible they have got it wrong again?