The event Maus was understandable back in 2021 after the major nerf that made it the rarest tank to find, and I believe the only tank to no longer appear in the junkyard.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3121854055


Should devs change the rarity because based on historical records:
1) Little Willie Only 1 was ever made - full stop. But far easier to find in game then maus.
2) Maus saw 2 built, with 7 more hulls/turrets/barrels/etc. fabricated (just needed wiring/hatches/etc installed) with armor plate cut to make 15 hulls 7 turrets and enough armor sheets to make 30 more maus. Rarest drop in game and blocked from junkyard.
3) KV-2 saw 210 made and only a few survived the eastern front.
4) Tiger II "king tiger" saw 492 made.
*** All other tanks in game had 500 or more made, usually thousands made. ***
5) Goliath (303=gas engine) Over +7,500 made. But in game - as rare as Maus!

And for fun I'd like to remind people 1 Maus was sent to combat the soviets. However it broke down before reaching the front lines and ended up getting destroyed by its crew.
With that in mind, the holiday event and being Christmas eve I'll link this 2013 video.
https://www.youtube.com/watch?v=iDnLG35yK7o