https://www.openstreetmap.org/node/8248716925/history

- Signed "SIPTU", not "SITPU" on lower building part and official website.

- This looks like a trade union, which seems to be tagged office=union. Not sure if it also qualifies as ngo but the union tag probably takes presidence as it's more specific.
https://wiki.openstreetmap.org/wiki/Tag:office%3Dunion

- Add contact tags
operator:website=https://www.siptu.ie/
operator:wikidata=Q7455836

Mapillary until 2019 (obscured by wall on 2020 imagery)
https://www.mapillary.com/app/?pKey=503023041135959&focus=photo