I was testing the one that says 4R7 on the inductor. I think the markings on the picture are just faded and don't show up at the camera angle, I bought all the boards at the same time. FWIW, I had tested these on the bench before I made the little top board, and I was happy with the performance.
I never spent any time analyzing the circuit or the parts they used, I just wanted a working small board. The first one that was even smaller was a problem as they rated it at 23 volts, and I did cook one. So I went with this board rated at 28 volts, and I've never had any issues with it.
Thanks for the info and being patient. Not sure what was up with my module. The offer's picture showed the 1584 chip and 4.7 uH inductor but neither is marked on the actual board. And it wouldn't be the first time I received small electronic modules populated with the wrong parts.