The guy in the picture is this guy:
http://en.wikipedia.org/wiki/Sultan_Qaboos
In 1970, he was started his reign.
In 1970 the country was also renamed from Sultanate of Muscat & Oman to just Oman.
I'm not sure what it commemorates tho, i can't seem to find what happened in 1980 in Oman. Maybe it's just a 10 year reign commemorative token ? We'll wait for someone who can actually read arabic. :)
Also, i'm curious, is it normal in that region for intervals to be written 1400 - 1390 instead of how we write 1390 - 1400 ?