grandfather

Hello again folks. Continuing the search for my Norwegian grandfather, Edvard Martin Eriksen(1865-1930),i have his signed"Oath of Allegiance"in Warwick, Queensland dated 8/3/1888 The only ship arrival prior to that date is for a Martin Eriksen, on the RMS "Jumna",out of London, leaving 8/2/1887 and arriving in Brisbane on the 6/4/1887. The birthdate for him is given as 1869.I have tried unsuccessfully to find out if they are one and the same. The next record of Edvard, is in Sydney in1892. Can anyone tell me the way to go from here. Many thanks. Ross Erickson