Saw this for the first time this month.
Its a photograph of the Project SWORD Booster Rocket used as part of an ID competition in SOLO comic from 19th August 1967.
Its even the answer SOLO were looking for. Its the odd one out!
The pictures was recycled from a previous showing in SOLO as part of the Project SWORD Identification Guide.
I wonder who won the 40 JR21 Thunderbird 4 toys? You?