Page 16 - Frank Walton GB Queen Elizabeth II Wildings

Dollis Hill Phosphor Trials

The trials were carried out between 1959 and 1972 at the Post Office Research and Development Centre at
Dollis Hill in London. The objective was simple: to develop inks that could be detected automatically by sorting
machines to enhance the operational handling of mail. The development team was headed by a research
chemist called Charles Forster. Trial mail was sent through the normal post to him.

2½d with two yellow phosphor 3d with one 4mm centre blue
bands on St Edward’s paper phosphor band printed over the ink
One of 36 recorded. RPSL Cert. Crowns watermark paper
Not listed by Klempka 3d with all-over blue phosphor Klempka Type DH36
No watermark
Klempka Type DH31

3d with all-over blue phosphor
No watermark
Klempka Type DH31

2d with strong all-over green
phosphor on the top half of
the stamp, but no phosphor
on the lower portion
Not listed by Klempka