Interesting puzzle. The 22G00000 engines were fitted into Land Rovers for the Australian market from 1983 onwards, but these were low compression engines, circa 8.13:1. Looking closely, next to the 5, there appears to be an 8. I would be more inclined to think that the 9.75 has been added at a later date, for one reason or another. The digits do not reflect coming from the same set of punches either, but there may not be nothing in that.
Ron.