u/Blackspine_collector

So, I've been collecting the SF Masterworks black spines for a while, quite happy with it so far, and recently got myself a copy of FMT,TPS - However it seems my copy doesn't have a number on its spine.

Is this a misprint? A reprint? A knockoff? I've no idea. Can't imagine one book in a series of numbered books just wouldn't have a number so I'm at a loss