The Australian Defence force were not big on giving medals.(I only have seen uniforms of US military in shows on TV and appears that some have quite a collection.)The only other involvment with the US were some "Kangaroo" excercises in the North of Australia K83 etc,and obviously dress uniforms etc were not seen.
The above medal only recognises 4 years continuous service.They don't have clasps for 8,12,16 and 20 years etc,or not that I know of.
The only other medal for service carried out was the Defence Service Medal,now the Long Sevice Medal,changed in 1999,extra clasps for longer service are available.This medal is for fifteen continuous years of service.
The catch word here is continuous service.
When I first joined (as an Army Apprentice) nearly all my instructors had Vietnam Campaign Medals,cooks,Q personnel and nearly all ranks,as the years progressed it was only the long stayers and eventually they retired as well.
Now with Australia's involvment in Timor,Iraq and the Solomon Islands etc there are more opportunities to go overseas and also depending on your area of operations gain recognition for your services.