Oman Proof Set 1990 (AH1411) a 6-coin set includes 20 Omani Rials 1990 KM#98, 100 Baisa KM#80, 50 Baisa KM#79, 25 Baisa KM#78, 10 Baisa KM#77, 5 Baisa KM# 76 FDC in the red presentation case of issue, unlisted by Krause, Rare. The standard sets of this year have the 2 Omani Riyal instead of the Gold 20 Riyal, and these sets come in a green box

Estimate: GBP 1000 - 1200