A Grave Mystery

This is the gravestone of Alexander Dun(n) Smith in Toowoomba Cemetery (Presbyterian Section 1, Block 3 Allotment 40). He died 2 May 1877 at Emu Creek, on the Darling Downs.

Here is the mystery, back in the days when you could read it, this stone was transcribed, and it says "Native of Angus"! 

But, I found Alexander in the Old Parochial Register for Barrachan, Mochrum, Wigtownshire, Scotland (around 320km or 200 miles away), being christened 3 October 1823, he was the youngest of 7 children in the family, all christened at Barrachan, to Francis Smith (a weaver) and Agnes (nee Young). Alexander's wife was Helen (nee Turner).

I have a couple of theories:

1. The stone was originally made for someone else, and the family was too poor to have another made (in this case, why not have the incorrect text erased?), or
2. Angus is where his father Francis was from, and so he felt the family was from there..?, or
3. Alexander was actually born in Angus, and his family travelled to Barrachan for the christening (I don't feel this could be correct as all his elder siblings were also christened in Barrachan).

I would love to hear of any other theories, and any ideas of how I might prove/disprove them.

So far, I have been unable to trace the marriage, deaths or births of Francis or Agnes. Although, there is a possible marriage of a Francis Smith to Alison Young, St Cuthbert's Edinburgh, 6 March 1805, which is before any children I can find.

This is the timeline for Alexander:

Year	Date	Event	Age	Location	Comments
1823	3/10/1823	Christening	0	Barrachan, Mochrum	Father Francis, Mother Agnes Turner
1824			1
1825			2
1826			3
1827			4
1828			5
1829			6
1830			7
1831			8
1832			9
1833			10
1834			11
1835			12
1836			13
1837			14
1838			15
1839			16
1840			17
1841	4 Jun 1841	Census	18	Auchengellie Farm	Servant to James Muir
1842			19
1843	4 Dec 1843	Marriage	20	Mochrum, Wigtownshire	to Helen TURNER
1844			21
1845		Birth of Child	22	Whithorn, Wigtownshire	Robert SMITH
1846			23
1847		Birth of Child	24	Symington, Ayrshire	James SMITH
1848			25
1849			26
1850			27
1851		Birth of Child	28	Riccarton, Ayrshire	Alexander Turner SMITH
1851	31 Mar 1851	Census	28	Riccarton, Ayrshire	Head of Household
1852			29
1853	26 Feb 1853	Emigration	30	Australia	with family on “Agricola”
1853	13 Oct 1853	Birth of Child	30	Ipswich, Australia	John Turner SMITH
1854			31
1855		Birth of Child	32	unknown	Helen SMITH
1856			33
1857			34
1858			35
1859			36
1860			37
1861			38
1862			39
1863			40
1864		Electoral Roll	41	Ipswich, Australia
1865		Electoral Roll	42	Ipswich, Australia
1866		Electoral Roll	43	Ipswich, Australia
1867		Electoral Roll	44	Ipswich, Australia
1868	16 Sep 1868	Land purchase	45	Aubigny, Queensland
1869			46
1870			47
1871			48
1872			49
1873			50
1874		Electoral Roll	51	King's Creek, Aubigny
1875		Electoral Roll	52	King's Creek, Aubigny
1876		Electoral Roll	53	Emu Creek, Aubigny
1877		Electoral Roll	54	Emu Creek, Aubigny
1877	2 May 1877	Death	54	Emu Creek, Aubigny