The Last Waffenträger: Event Guide

Dwigt: You can earn 3 types of footlockers and each of them contains special different rewards.Harriers’ Footlockers (common) obtainable from missions in the T-55 Thunderbolt Engineer’s Footlockers (uncommon) obtainable from missions in the WT E100. These 2 will have unique collection items that will help you progress through the event, earn keys for the WTE110 and earn more rewards. Special Footlockerobtainable by destroying a WT E220 or from the premium shop. When you open it you will receive 100 gold and a random reward. If you don't like the reward you can still reroll it for 100 gold (1st reroll is free) then 250 gold for the second reroll...  

Dwigt: You get the 3k bonds after completing the progress bar and missions and opening Harriers’ and Engineer’s footlockers. So you're getting additional rewards and a chance to get Special footlockers that contain the T77, gold and other premium tanks.