Bit More,
From a submitted tree, (yes I know

) Ireland, Monaghan ? birth 1781 of Owen McNally.... married to a
Catherine MECADUM around 1800, three children, last one in 1812.... no further trace of the couple after 1812.... although at least one child stayed in Ireland and married there; another went to Canada and married there...
However, on off-chance anyOwen McNally may be part of Catherine's "impediment" here's one
Owen
MCNALLY as a crewman in
January 1823 on Elizabeth & Mary to or from
MACQUARIE ISLAND and
he was not born in the colony . There's a

"
Free by Certificate no" Umm.... 16/2 (and other digits, hard to read, could be
16/268 or even 4 digits...
EDIT to note, I think the "16" in the Certificate number refers to the year 1816, being the year the servitude/sentence of transportation was complete... Cheers, JM