Joyride Studios/Halo 1 Series 5
From Halopedia, the Halo wiki
It was known to have been perhaps one of the rarest figures to be produced.
On each action figure unit, Joyride has included a serial number, which allows you to find out when the action figure was created. The date code has four numbers followed by 'SS' actually stamped or embossed in the cardboard. The first three digits are the date the product was made, and the fourth digit is the year. For example: 2653SS means the product was manufactured on the 265th day of 2003 (9/23/2003).