Early Experimental and Inland Branch Duplex Cancellations, by J Parmenter.

Published by London Postal History Group, 2007.  Sp/B, 67pp.

A study of the Inland Branch Duplex cancels, using the Dubus classification system (a guide to the new and old classification codes is included).  The cancellations of the Pearson Hill Experimental Machine, Pearson Hill Trial Machine, Pearson Hill Parellel Motion Machine, and Rideout Trials are also discussed.  This priced catalogue contains a rarity guide and a table showing the dates of use of the postmarks.  Illustrated in colour.