Thanks to all those who responded direct to my request for information about the Pilkington Gibbs heliochronometer.
For information - nobody has responded that they have seen another half size instrument, nor has anyone reported a serial number higher than 944. Mike Shaw http://homepage.ntlworld.com/jmikeshaw/ N 53º 21' 24" W 03º 01' 47" Wirral, UK. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.307 / Virus Database: 168 - Release Date: 11/12/2001