Manly was ranked in the top 50 as recently as the mid 70s. This was more a reflection how poor 2nd (3rd & 4th) tier golf was in Australia back then.
Apparently, MacKenzie made some alterations to the courses bunkering when he was in Sydney through his contact with Eric Apperly. Apperly was a member there for years, as well as famous Australian Pros like Joe Kirkwood, Jim Ferrier & Ossie Pickworth. It also had the NSW Open (When it was a reasonable size tournament) quite a few times from the 30s through to the last time in 1975. It also had the Australian PGA Championship just after WWII, as well as a few other local events.