Dollis Hill ST5(4)d Yellow all over phosphor Strip on Cover

Great Britain has never knowingly issued stamps with a Yellow phosphor reaction although some Machin issues had a Yellow phosphor reaction due to ink contamination. The Dollis Hill archive contained a few stamps and a few covers where Yellow phosphor had been used. Forster stated in his notes No watermark paper sized with Yellow emitting phosphor good emission but condemned as possibly toxic. The stamps are of Light Reddish Brown appearance and are usually a blotchy print. The distribution of the Yellow phosphor is patchy. Strip (x 3) 2d Light Red-Brown with Yellow all over phosphor used on cover from Gloucester on 27 December 1971. Ex Edward Klempka Author of the DOLLIS HILL FIND. illustrated on page 21. Cat 1500+++ pounds