if you look in the trim and colur charts here http://www.vauxhallviva.com/thecars/hccodes/1971trim.html yuo can see that a two door SL saloon is a model 93511, and the only blue listed with white stripes is wedgwood ... the owner should be able to confirm this as the chassi plate on the front inner winner wing will have the follwoing code '5BL'.