R1-G4 was one of the many droids being sold by the Jawas to Luke Skywalker and his family. R1 was not one of the 2 selected droids and was later probably taken by Stormtroopers and put into Imperial use. Once he was taken he was probably destroyed on the 1st Death Star. This is not known for sure though. The R1 Units were some of the first astromech droids to be manufactured so this unit is probably very old.