As Jethro mentioned above, minor casting difference shown in your picture. Looks to be just a thicker bolt flange web and thicker wall of casting. Overall that is immaterial if it fits and does the task it's meant for. It will work in your application and that's all I think you are asking here.
He mentioned worn molds from repeated use , I don`t think a redesign of the housing? Just retooled back to spec.
As long as it works. I`d bet the one installed in the engine now has the open fined back version of the same pump.
