Dollis Hill 3d Block (x 15) blue all over phosphor No Wmk

Annotated on the reverse 39 Blue phosphor in Green water and polyvinyl alcohol very good 14.1.1959.Edward Klempka said. Fifty years after the application of the phosphor ink the colour of the afterglow may have changed. Forster refers to the colour of the phosphor ink used for the 3d values as Blue and I have used this description regardless of the visual Greenish-Blue colour. Ex Edward Klempka Author of the DOLLIS HILL FIND illustrated on page 28. Cat 5250 pounds