If you open the West Iron Door 90 degrees (as it's usually found during business hours), then the sun on the door is in a square with the similar carving out of stone on the Western edge of the King's Stone. This shows the CAD mapping of A and B and below will be pics of both:
A: Analemma on West Iron Door
B: Analemma on West edge of King's Stone:
The radius of the circle or edge of the square seems to be about 726 inches.