It's a variant on the more usual plain white/madras/squiggle shirts, so possibly quite rare. Proof that it was an original pattern is in Arthur Steel's 1981 photo of Westwood outside World's End (photo from https://arthursteel.co.uk/gallery/rare-black-and-white-photograph-vivienne-westwood-worlds-end-pirate/). The shirt for sale is identical to the one worn (by Jordan?) in the window. 

The shirt's made of semi transparent cotton (or muslin), with dropped shoulders, very wide sleeves and a red/burgundy and white striped collar and bib front, edged in broderie anglaise lace. The cuffs are also edged in broderie anglaise. They're long but meant to be doubled over (though I always preferred to wear them long). The shirt is unisex and unsized, but long and as voluminous as all the original 1981 versions. The label is marked World's End, born in England.

The shirt's been worn, but is in pretty good condition for its age, with just some fading of the red stripes and a darned hole near the hem at the centre front (see photo). 

I've included a domestic postage price only. Please contact me if you want an international delivery price or for any additional photos or information.