Being a post war HSAT will mean the price will not be as great as if it was WW2. If selling on ebay these post war ones seem to go for anything from £185-£250. Yours seems to have lost the rubber around the liner so might not fetch a great deal. Good luck with your sale.
The liner is dated 1955, so that part at least is post war, as is probably the rest of it, though this is not my area.
Whatever its just an opinion.
Thanks for the quick replies and info. It is a huge help in selling it. Thanks.