I'm guessing, but I would have thought that by that period, a 'proper' seat harness would have been used. The photo you posted looks like a good guide, but I think that it is a more recent shot, with a 'modern' harness, just going off the overall style and materials, and the blue web strap on the 'anti-g' crotch strap. The actual harness would probably be very similar though, maybe a slightly different colour perhaps, but small detail differences would not be noticed in this scale.