Having finally bitten the bullet and paid up for the death certificate of Alexander Sim, who died in 1892 in Wallasey, I am not really surprised that I am not much the wiser. In particular I still lack sufficient proof that he is Alexander Sim junior of Sim's Mills, Collooney, and (estranged) husband of Jane Mary Allan Aitken.
The informant was William John Coffee, in whose household Alexander Sim was a boarder in both 1881 and 1891. In 1881 Alexander Sim was described as 'Merchant's clerk'. In 1891 he was 'Retired miller'. In his death certificate he is described as 'formerly a foreman Dock Porter'.
In 1881 and Jane Mary, living apart from her husband, describes herself as married, and in 1891 and 1901 she says widowed. Alexander says in both 1881 and 1891 that he is married.
(I did look into William John Coffee to see if he was some sort of relative but it looks unlikely. WJC was born in London in 1825, son of Matthew Coffee and Elizabeth Wyatt. He moved with his family to Liverpool before 1841. In 1851 WJC was living in Liverpool with his sister Alice and her husband John Bibby. Later that year he married Hannah Hewitt. In 1851 he was described as an 'annuitant'. In 1861 and 1871 he was a 'licensed victualler' and in 1881 and 1891 an 'emigration agent'.)
Does anyone have any ideas of any other source that might provide evidence that the Alexander Sim who died in 1892 was indeed the husband of Jane Mary Allan Aitken?