The Irish Lord Lieutenants lived in the Vice Regal Lodge (now Áras an Úachteráin) in the Phoenix Park, Dublin. A Lord Lieutenant was the representative of the British Monarch in Ireland.
This button is of two piece construction, all gilt survives. It measures 19mms in diameter.
The button is well maker marked to reverse:
“JENNENS & Co. LONDON”. (Probably pre 1860 as after that date, Jennens marked their button reverses with the Prince of Wales plumes).