Dears,
Many thanks for your comments and feedback.
All coins are fine gold. Below details for each coin:
1.
- Sindibad Voyage 1980/1981 coin 2003 year(certificate of Authenticity comes along, 200 coin in total were minted. I couldn't find however on the website of Central Bank of Oman this Commemorative coin) -156gm on scale, 6.5cm diameter.
2.
- Somali Republic $500 coin 2000 year - 37gm on scale, 3.8cm diameter.
3.
- Somali Republic $250 coin 2004 year - 23gm on scale, 3.2cm diameter.
4.
- Holy Prophet's Mosque 1409(1989) coin KSA - 15gm on scale, 3.2cm diameter.
5.
- DMCC Dubai coin 2007 year - 18gm on scale, 2.4cm diameter.
6. 
- DMCC Dubai coin 2007 year - 8gm on scale, 2.1cm diameter.
7.
- Face with Arabic (cannot read) - 4gm on scale, 2cm diameter.
8.
- Elizabeth II, Australia 2009 year - 3gm on scale. 1.6cm diameter.