Once devs showed odds in their discord ( https://i.imgur.com/qPsI86G.png ), that gave me hint how to calculate odds for eu version, so kinda "real" drop odds for common boxes
As You can see chance for getting Uncommon Attachement keep on growing in 2018, why? Because they kept same items odds while adding a bunch of items for that cathegory and lower for others, which lead to change from 30,3 to 53%
Only in april 2019 they decided to rebalance items, lul.
For supperior box, I need to recalculate it.
Full table is here, where you can check odds for every type of item in almost every update. My own opening stats show same pattern.