I've never seen it before this house either, although the well guy around here has. They are both 4" pumps, it was real fun replacing the pond one this spring as we pull the house one too.

The only requirement was that he installed a check valve to prevent backflow from the pond to the well per code. He said we could do a check valve or a air gap, we opted for the valve. I'm not sure how it could ever backflow as the feed from the well head is about 20ft higher than the pond, but code is code.