This is a set of the first series of Orchid dollar notes in all 4 varieties, signed by Singapore's first 3 Ministers for Finance.
Mr. Lim Kim San (Chinese: 林金山; pinyin: Lín Jīnshān; Pe̍h-ōe-jī: Lîm Kim-san)
Dr. Goh Keng Swee (simplified Chinese: 吴庆瑞; traditional Chinese: 吳慶瑞; pinyin: Wú Qìngruì; Pe̍h-ōe-jī: Gô͘ Khèng-sūi; 6 October 1918 – 14 May 2010)
Mr. Hon Sui Sen (Chinese: 韩瑞生; pinyin: Hán Ruìshēng; 1916 - 1983)
The first variation was signed by Mr. Lim Kim San, the second by Dr. Goh Keng Swee and the last two by Mr. Hon Sui Sen (with seal and without seal). The variety without Mr. Hon's red seal is not an error note but a less common note variety being printed. Out of all these notes, Dr. Goh's variety was printed with the least numbers.