https://www.rugbyleagueproject.org/players/jack-jeffries/summary.html
It appears to be 14 March that he passed.
http://www.prattenparkmagpies.info/?page_id=18925
https://www.zerotackle.com/ex-magpies-hooker-jack-jeffries-passes-away-aged-68-219767/
Just need to check his year of birth Pratten Park Magpies say 1956 but Wests Archive say 1957.
Following Jack's memorial yesterday it was confirmed his DOB was 6/4/1956.