What Airfix model is this?
It is a relatively early Mirage IIIc. You can tell it from other common modifications by the longer rear fuselage, which accommodates the longer afterburner of the older Snecma Atar 9B engine.

The exhaust nozzle on your model is closed indicating military power. On most photos you will see it wide open (it has two buckets on a hinge, and a horizontal gap is clearly visible).
I know all this because not too long ago I built a similar model, but with a smaller 1:100 scale.