I found this in one site:
"Dec. 14 is the date when the Windows 10 rollout begins in Poland and it will target the Lumia models 830, 735, 640, 635 and 630. The second wave of updates will occur at the beginning of next year. On Feb. 1, 2016, owners of Lumia phones 1320, 1020, 930, 925, 920...