Australian WW1 Trench Art - Rising Sun Serviette Rings

I just got given this set of serviette rings to add to my collection. At this point all I know is that they were purchased in 1972 as silver plated trench art from World War 1. The previous owner came to this same conclusion from his own research. I have not been able to verify this as of yet but it's not at the top of my priority list at the moment as I have no wish to sell them at this point in time. I think they look great and can't wait to find a nice place to display them. That being said, it would be nice to know a little bit more about their history.