$10 is a sympathetic price for any smock, even this one. As far as the arm patches go, they are called Drop Zone flashes, they were made of ribbon, linnen, felt and various fabrics, according to Charles A. Edwards' Drop Zone flashes of the British Airborne forces p. 16. Variations existed because of local procurement. Their size is listed as 2 1/2 x 2 1/2 inch. The only problem with these specific flashes is that they were worn from 1961 onwards, and I think this type of smock was replaced in 1957 by the 1957 pattern Denison smock, which had a different coloured camouflage print. See ebay object number 250056389616 for an example. The cuffs and full-length zipper could have been officers alterations, the back could have been torn and repaired? The smock has enough original details to exclude the possibility of being tinkered with by costumers, the most significant oddity is the different panels on the rear, now why would a costumer do that if he/she has an original smock to start with? The only movie smocks I'm aware of were those made specifically for A Bridge Too Far, and they were of a much better overall quality than this one. It would be interesting to see additional photos of the front laid out flat, and the inside of the front and rear. Fougasse1940.