The subject is not identified, and not much can be seen of his clothes apart from the tam-o-shanter. However, the style of the portrait, the design on the reverse of the card mount, the thin card used, and its square corners, all point to a date of around 1869-1874.
Robert Sands was born at Atherstone, near Coventry in Warwickshire, around 1812-1814. Nothing is known of his early life, until the birth of his first child, a daughter Sarah Ellen, by Elizabeth Lyne at Soho Square, London on 11 January 1845. A son Edward was born to them at St Martin's Lane just over a year later, and both children were baptised at St Martin in the Fields, Westminster on 5 April 1846. Robert was shown living at 276 Kent Road, Newington, Surrey at the time of the 1851 Census, with a "wife" Eliza, twelve years younger than him, but the two children were not with them. He described himself as a comb-maker and agent. However, it appears that he only married Elizabeth (or Eliza) Lyne at the Old Church, St Pancras, London on 14 January 1855. (Elizabeth was born at Bath, Somerset, son of John & Mary Lyne, or Lines, and baptised there on 19 January 1823.)
The reverse of the carte de visite shown above claims that the firm had been operating since 1851. David Webb's photoLondon database shows Robert Sands to have started working at 3 Postern Row in 1854, and nearby at 79 Minories in 1856. It seems likely that they moved from Kent Road, Newington, Surrey, where another son William was born in late 1852, to Postern Row, Tower Hill, London, prior to or soon after their marriage in early 1855. A fourth child Sophia was born in late 1856 or early 1857 - her birth was registered in Hackney. A report in The Morning Chronicle (London, England, 16 May 1857) refers to "a photographic artist in Postern-row, Tower-hill," which is probably Sands.
By April 1861 the whole family, including all four children, were living at Postern Row, and Robert Sands was shown as a "Dealer in Photographic Goods employing 4 Men in Photography." Their eldest child, Sarah Ellen, died a few months later, and towards the end of the year Robert was declared bankrupt, spending some time in Whitecross Street Prison before the bankruptcy was discharged. The newspaper reports and the London Gazette describe him as "of No. 3 Postern-row, Tower-hill, and of the Minories, photographic artist and dealer in pictures and curiosities." (Daily News, 9 November 1861; The Morning Chronicle, 29 January 1862; London Gazette No. 22563, 8 November 1861, p. 38; London Gazette No. 22576, 13 Dec 1861, p. 43) The photoLondon database states that Robert was succeeded from 1860 to 1862, at both 3 Postern Row and 79 Minories, by an artist named Emil Folk (1830-1887), but it is possible that Folk was merely employed by Sands.
Robert and Elizabeth had a third son, Robert Edward, born at Postern Row in late 1862 or early 1863. It seems likely that their older sons took over the photographic business in the mid- to late 1860s. The photoLondon database has first Edward (1866-1868) and then Edward & William Sands (1868-1869) working as photographers from 3 Postern Row. This was suceeded by the Co-Operative Photographic Society, managed by Edward Sands, from 1870 until 1873. The 1871 Census shows Edward & daughter Sophia both working from home as photographic artists, and their father Robert is shown as a commission agent. Edward Sands registered a photograph of the George Tavern, Trinity Square (at the end of Postern Street), City of London, in December 1869.
Sophia Sands married a tailor from Germany, Fredrick Kopieski, the following year. They had four children before Sophia died in 1882, at the age of 28.
From 1874 until 1882, the photographic business was operated at 3 Postern Rown under the name, Robert Sands & Son. The photoLondon database has this son as Robert Edward, but he would have been too young for at least some of this period, so it is likely that one his older brothers William and Edward were working with Robert Sands senior. Robert Sands died in late 1882, at the age of 69, and the business was presumably taken over by William and Robert Edward, who continued from 1883 until 1885. William Sands died in 1900 (Whitechapel Registration District), aged 48, and Robert Edward Sands died at Poplar in 1903, aged 42.
The photoLondon database suggests that Edward Sands, who was also a portrait painter, was living in Melbourne, Australia from 1882 until 1900. However, I've been unable to find any independent confirmation of this.