I've noticed! Jim Fitzpatrick's no mug & knows a bit about 'Celtic' stuff.... ;o) Looks like it's Newgrange influenced - at least on the horizontally orientated stone(s).
Great album, too - especially the title track (imo).
I have a great fondness for the Eric Bell/pre-Vertigo Thin Lizzy, because it is very different from the later sound. Which I also have a greet fondness for!
There's a Peel session from 1974 with Gary Moore in the band that bridges the gap beautifully.
This reply has nothing to do with Antiquaria - apologies.