Two modern scholars have translated the section of the Auraicept that tells us how to read Ogham. In the translation of Calder (1917):
“This is their number: five Oghmic groups, i.e., five men for each group, and one up to five for each of them, that their signs may be distinguished. These are their signs: right of stem, left of stem, athwart of stem, through stem, about stem. Thus is a tree climbed, to wit, treading on the root of the tree first with thy right hand first and thy left hand after. Then with the stem, and against it and through it and about it.”
In the translation of McManus (1988):
“This is their number: there are five groups of ogham and each group has five letters and each of them has from one to five scores and their orientations distinguish them. Their orientations are: right of the stemline, left of the stem-line, across the stemline, through the stemline, around the stemline. Ogham is climbed as a tree is climbed.”
The ‘root’ would be in the ground. The visible remaining steel screws (guess) suggest that it was fitted upside down and held in place by these screws attached to a ground scaffold of probably steel with the ‘roots’ in the air...
Asking for advice on dendrochronology for dating would merely suggest the age of the wood and not the engraving on it. It is too thin with a neatly cut back with Ogham type symbols raised to be considered as ancient. The removal of wood to leave raised Ogham is a lot more work than the usual method of carving the symbols into the parent material - wood or stone...
The alphabet is a mix of two types with one type using the leaning half line style. This is shown on the modified image with the comment. It looks good but it does not say anything. A movie or tourism prop that was discarded after use, nice find however.