Patentlog. Walker's 'Trident' Electric Mark III Ship Log, gepatenteerd in 1930, door Thomas Walker & Son Ltd. Birmingham Engeland.
Inscription
signatuur vervaardiger: Thos Walker & Son Ltd. Birmingham opschrift: Walker's 'Trident' Mark III Made in England Walker's 'Trident' Electric Ship-Log Cherub Rotators Used Trade - Mark T.W.