We were lucky to find this uncommon early 1970s Zodiac Spacetronic with an exhibition case back! We are not certain, but this may have been a dealer’s sample watch with the see-through, signed case back showing the movement. We just had the ESA Dynatron 9150 movement cleaned and it is very accurate. The dial, hands, and winding crown are all original. The original stainless steel case measures 34mm across and is hexagonal in shape.