I think you're right, Richie. I couldn't find a photo of the 3213-3218 series GSV (1978). This seems to be 3216TL and they were built from earlier coaches, likely the 2130-2136 series composites CIE built 'laminate' stock. These were the first composites to be built on the longer 61'6" chassis whereas the 2124-2129 were on the earlier 60' chassis. However, I'm not certain of that. The vans apparently ran on GSR bogies and were only 9'6" wide so it's possible they were converted from something even older although I don't know if anything prior to that had a 61'6" chassis. If anyone has any info on this, I'd be interested to hear. Many thanks for that photo, Richie!