I have just had a look at my copy and it is also clipped, the 7th impression is priced at £1.75 and not clipped, so it looks like they had dust-jackets left over with a £1.75 price on them, which were clipped for this impression. The 9th impression is £2.50 in my copy.
My 8th impression has a printed £2.00 label on it, so is slightly different.