Transforms for the early Kerr metric

The concept and usage of the word 'metric' within General Relativity is briefly described. The early work of Roy Kerr led to his original 1963 algebraic, rotating metric. This discovery and his subsequent recollection in 2008 are summarised as the motivation for this article. Computer algebra has confirmed that nominal transformations of this early metric can generate further natural algebraic metrics. The algebra is not abstract, nor advanced, and these metrics have been overlooked for many years. The 1916 metric due to Schwarzschild misled Kerr into seeking a similar metric for rotation. The philosophy of astrophysics for Penrose, Hawking and others would have been very different had they used the two lost metrics.