Heard from a friend:

2013 Joined service, GEO1.1 C
2014 GEO1A1 (promotion - cohort) B
2015 GEO4 (promotion) B
2016 GEO4 C+
2017 GEO4 B
2018 GEO5 (promotion) C+
2019 GEO5 B
2020 SEO1 (promotion)

Fast?