Thanks! I love the restraint they showed with text and visuals on dial 🤣 - only 3 lines and I think this was the first Spring Drive with power reserve on the back.
9R31 was first normal price SD with rear PR. And OP’s SBGY003 was the first steel watch with 9R31. The other being the rose gold Y002.
Previous to that, the caliber 9R01 was only in precious metal middle five figure watches. And the concurrent with 9R31, the 9R02 likewise came only in precious metal cases.