I would be inclined to lean towards 1948/9 principally because one of the buses on Eden Quay looks like one of the 289/98 batch under the magnifying glass but this is not conclusive. Before that I would have opted for the period 1945 onwards but as 302 says, GNR had only 10 double deckers prior to 1948 and it is unlikely, but possible, that 4 of them would be on Eden Quay together. The first one, barely visible, is definitely one of the 62-67 batch, one of which (62) was Dublin's first modern double decker. Other reasons why I was leaning towards the earlier period was the very large areas of white paint on the wings of both the R and the A which can be seen at Burgh Quay, I think this feature had been modified by the later 40's.

The interesting thing about this photo is that it appeared in a tourism brochure in the 1970's!