Regulation 21—Marking Application.(1)  On receipt of an application the Registrar shall mark, on each document making up the application, the actual date of receipt and the application number consisting of the letters GH, slant, the letter P, slant, the last  two numbers of the year in which the initial papers were received, slant, and a five-digit number alloted in the sequential order in which applications are received.(2)  Where any corrections or other later filed documents are received on different dates, the Registrar shall also mark their actual date of receipt in the appropriate place of the request for the grant of the patent (Form No. 2) in the Second Schedule.(3)  The application number allotted under sub-regulation (1) shall be quoted in all subsequent communications concerning the application.