not a military vehicle but one of the era that Boards.ie members may have come across. Possibly used after some of the military actions of the period and appears to have been in the funeral cortege of Michael Collins
I think the IK registration was a Dublin County code used from 1903 to March 1927. Pembroke Urban District Council's fire engine purchased in 1910 was numbered IK 686. Both vehicles are handy as dating reference points.
The Irish Times Book of the Century by Fintan O'Toole has a nice photo of IK 686 with other Fire Brigade vehicles IK 1614, IK 1413 and IK 1414.
From Tim Pat Coogan and George Morrison's book The Irish Civil War with a huge collection of photos :
p 16 a Crossley Tender outside Harcourt railway station carrying Auxilliaries, IK 3033
p84 UVF Motor Cycle Corps - OI 282, IJ 767, BO 1076, OI 2615, OI 497 and then some
p 182/3 Lancia armoured cars pictured at the start of the Civil War next to the artillery piece firing on the Four Courts are registered as OI 9213 (chalked with "We have no time for Truceleers") and OI 9173 (labelled Ashtown). They appear in this image
Ralph Riccio's "AFV's in Irish Service since 1922" has a nice photo of the "Fernside" armoured car with an anti grenade mesh on top.
Nice image of a Crossley tender NC 1785 here
A Lancia in Belfast with anti-grenade mesh