A friend of mine asked if I'd go with her to the Antiques & Collectibles Market at Avondale Racecourse today -- I'm glad she did. I can thoroughly recommend it to anyone nearby who'd like to have a bit of a browse. Not everything was high-end price either -- I was able to buy things there for less than $10 per item, most way less.
The booty I brought back home includes these two screen advertising plates. Screens Advertising Limited was a company tasken over by Kerridge Odeon as their firm for obtaining ads and preparing the plates, which are a 3 1/4 inch square slide. According to Wayne Brittenden in The Celluloid Circus, these took some weeks to produce, with the finished product a tinted transparency sandwiched between two sealed sheets of glass. Per cinema show, there could be around 40 or so of these slides, all manually projected from a carbon-arc slide projector.
Each screening per plate was around ten seconds -- any longer would crack the glass.
Come the 1970s, these slides were replaced by advertising films. My own moviegoing only began in the late 1960s at the earliest, so I would have missed seeing the ten-second slides.
Also found was this 50 year old pin badge for Sandringham's Edendale School 50th celebration. This year, the school (vastly different) celebrates its century. Cool to find this, though.