The plating of the penny, 1840-1864 a tabulation of the measured positions of the check-letters and other relevant data arranged for easy plate identification 
Brown, Roland.
Fisher, Harold W.(Harold Wolf),1903-
Great Britain Philatelic Society.
London Great Britain Philatelic Society,
[1972]
In 6 vols
The Roland Brown line-engraved plating gauge in pocket
Bibliography: p.312
Postage stamps
Postage-stamp printing