score:9
A sub-lieutenant of one of the Rifle regiments. Off hand, judging from his cross belt, actually a cartridge pouch belt - the cartridge box being on his back, I would place him in the 26-90 Regiments of Foot, The Cameronians (Scottish Rifles). With the 90th Regiment of Foot (Perthshire Light Infantry) forming the 2d Battalion of the 26th Regiment of Foot (The Cameronians) in 1881 (one of the many regimental amalgamations of the Childers Reforms), the new regiment became a Rifle Regiment and adopted the green jacket of the Rifle Corps initially with green trousers but soon in tartan trews of the universal pattern. In 1891 they adopted trews in the Douglas pattern. (Also see Bowling, A.H., Scottish Regiments 1660-1914, Almark Publications, 1970, page 20.)
The distinctive cross belt can be seen here, while the caption says Rifle Brigade, the gents are clearly displaying the Cameronian regimental badge, seen here, scroll down to the fourth display, on their cross belts. Another Cameronian officer, in review order, minus the braid on the jacket, so probably a little bit later, say, 1905, maybe 1908, can be seen here again with the distinctive belt devices. One might note the difference between the Cameronian belt devices and those of the Kings Royal Rifles here.