Hi Max, just checked Leslie Pinas 50s glass p.164 on labels & signatures. It gives a list of Orrefors Designer signatures which have a single letter to identify them by. It goes on to state that after 1980 two initials were used instead to identify these designers. The only one in the list with the initial D is for Ingeborg Lundin. However, the second initial used by Orrefors indicates the type of glass, but there isn't one shown with the letter R. (A = cut glass, E = frosted (satin ground), U = workshop made, smooth glass, Z = green lustrous glass and Graal-S or S-Graal = slipgraal). So it may well be the engraver. I too have a piece of Orrefors signed with the name Valentine, but members on the board felt that this was probably the artist who painted the flowers.
p.s. I like decanters :lol:
Regards - Anne E.B.