" With reference to the note by Mr. G. W. Groves (Bulletin No. 8, p.10), I find that the Duplex 'DB,' 'OR' and 'SP' were still in use in 1923, although my copy of the latter is in the month of January. I make the c.d.s. of these duplex marks to have an outside diameter of 19½mm. The large single c.d.s. (non-duplex) I have only seen for 'SP' dated 1924 and 1925. The diameter of the c.d.s. is 25½mm. and 'SP' 3½mm. high (duplex type 'SP' 2½ mm. high). All lettering is proportionately larger than the duplex type and the colour black. Should not the list also include 'CA' = CAYON?"