Volume 4 No. 24 of Science Fiction Adventures, published in January 1962. What's so darn special about it? Well it features the first appearance of J.G. Ballard's dystopian classic The Drowned World, which debuted in this issue of Science Fiction Adventures months before it was published in hardback by Gollancz – making this effectively the true first edition. (See this post for more.) It's a pretty scarce publication, with lovely Brian Lewis cover art illustrating Ballard's tale, and it's got a low starting price, so someone could potentially nab a bargain.
All of my latest eBay offerings can be found here:
Existential Ennui on eBay
Or by clicking on each picture for the individual auctions...