Here's what I think might be the origin of the Spacex Supply Force Mercury design. Not close in detail perhaps, but the general outline is certainly there. It's the 1959 XAB-1 atomic-powered bomber kit produced by Hawk, where I first came across the picture of the 1964 rerelease box as shown below. Seen from that angle, the similarity is pretty evident.
As the picture of the built model shows (picture used by kind permission of Allen B. Ury, who built this beauty) (1), the front and nose are particularly close though there are plenty of differences at the rear of course. But as shown by the little side-by-side I've made up (distorting and mirroring another of Mr Ury's photographs - see below), I think the similarity is again apparent.
And detailing such as the panel lines on the wings is again not identical but still quite similar.
As to the XAB-1 design, there's no information to be found on such a craft, just references to the Hawk kit, a subsequent resin kit produced by Fantastic Plastic, and a (nice!) paper model kit based on the earlier plastic kits. In fact, somebody on the Secret Projects forum quotes the original Hawk instruction sheet which states it's a "hypothetical" design "which -could- exist" (2). But with the Hawk kit having been rereleased in 1964 (and possibly somebody having a built model of it sitting around), plus the similarities described above, I think the XAB-1 is still a very valid contender as a design origin for the Spacex Mercury.
We can be certain the Spacex designers have seen the spacecraft above. It's from the same Fireball XL5 story drawn by Mike Noble as where the Nuclear Freighter origin is from. Starting in TV21 magazine #71, published 28 May 1966 (and where the image above is from the opening panel), the story is about a black pirate ship which XL5 is sent to hunt down, and which is revealed to be part of a scheme by the rogue state of Bereznik to capture various ships (including XL5) to steal their technology.
While generally similar in shape to the Spacex Mercury, the black ship is very different in detail. But it does have a more simple rear fuselage than the XAB-1, with an engine exhaust at the end like the Mercury has. It also has detail at the top of the tail where the Mercury has a small top stabiliser. And the pirate ship has a bulge at the front of its body, where the Mercury has one to help keep the plated front glued to the unplated rear. So who knows, maybe the pirate ship has played a small part in what the Mercury looks like.
1: More pictures of Mr Ury's XAB-1 model plus a brief bit of background can be found on his website. A further look at his other models is highly recommended - there's a brilliant collection of prototype aircraft and spacecraft to discover there. back to text