I went to download the latest SDK and discovered that the version number had been bumped from 1.43.0 to 23.0.0. Which seems like a giant jump in numbers, but I guess that there is some hidden logic behind this jump.
Once downloaded I checked the version number in the OVR_Version.h file. In this file the version number is stated as 1.55.0. The same number is also found in the LibOVR\Projects\Windows\LibOVR.props file.
So I guess the correct version number should be 1.55.0 and not 23.0.0???