The book has arrived and quickly.
Looking on page 108 (where the 1972 catalogue gives the pattern number 4025 for the 6 fl oz glasses) there is a photograph from the '72 catalogue of a Morven decanter, a jug and six different glasses. Judging by the proportions I reckon the glass I have here is shown on the right of the top shelf. On page 38 Mark Hill states that Morven was not made in Heather so this colour must be Peat (they were made in clear, Peat and Soot). The glasses match exactly.