I'm pretty sure that's a '67. Hofner experimented with a one-piece back in 63/64, discontinued, tried again in 1967, then ceased for a long time.
Every '68 and '69 I've ever seen had the more common two-piece back.
Mind you, as already pointed out, Hofner had zero interest in consistency and ran fairly large parts bins. It's quite possible that your bass has a one-piece back made in 1967 but which was not incorporated into an actual bass until a few years later. If so, then that would be the first example I've ever seen, but it's perfectly possible.
More importantly, that price for a genuine German-made Hofner is excellent [[i]trans. - "cheap"[/i]], regardless of the exact date. My lovely 1964 means that I really can't justify buying this, but GLWTS.