We know beyond a reasonable doubt that DY-100 Class S.S. Botany Bay
had some sort of artificial gravity generation system onboard ("Space Seed" (TOS))
We know that the key to this device most-likely was the recovery a Slaver stasis box which contained a 'flying belt' ("The Slaver Weapon" (TAS)). Alan dean Foster's novelization for this story suggests that the stasis box was recovered on Earth's moon. This suggests a point of discovery anywhere between 1968 and 1992.
Question: Assuming the above sources to be technically accurate, how and when was the first artificial gravity generator brought online and how was it first used in spacecraft and applications prior to the launch of S.S. Botany Bay