https://www.rugbyleagueproject.org/seasons/nswrfl-1975/round-21/newtown-jets-vs-canterbury/summary.html
All the Canterbury numbers you have listed including the reserve are shown in the video below, but with the Newtown numbers, there isn't a number 18, but there is a number 5 (see 1:54 scoring a try), so I am assuming Brian Robertson wore the number 5 not 18. All other Newtown numbers are shown.
https://www.nrl.com/news/2026/07/07/jets-v-bulldogs---round-21-1975/