Can items from the free cases be sold?

According to the author, no. The cases drop often through normal play and their loot cannot be sold, so farming them has no market value.

What rarities do character items have?

Only two: rare and legendary. Weapon skins have more quality levels.

Which weapon skin qualities dropped?

Only three of the five: blue (regular), gold (legendary) and starred. Gold and starred skins have no wear gradation.

Vault, Items & Cosmetics

KF2 Free Vault Case Drops: Statistics From 600+ Cases

A player opened more than 600 free cases in Killing Floor 2 and kept statistics, just for interest: the cases drop frequently through normal play and the loot cannot be sold, so there is no point in farming them. Opening 200 cases took more than an hour. For the vault itself see vault weapon skins by perk.

A grid of golden vault cases Vault cases waiting to be opened.

Rarity system

Character skins and accessories drop in only two tiers: rare and legendary.
Weapons have five quality tiers and several wear states, similar to CS:GO. From the cases the author only ever saw three tiers: blue, gold and starred. Gold and starred have no wear gradation.
Wear states seen: Battle-Scarred, Field-Tested and Mint.
The cases contain 14 standard weapon skins.

First 200 cases

42 legendary items in total, 14 of them character customization and the rest weapon skins (which are much better made than the character ones).

66 weapon skins: 33 regular, 11 starred and 22 legendary.
134 character items: 40 face paints, 17 uniforms (4 legendary), a staggering 29 pajamas, 8 glasses, 21 hats (7 legendary) and 8 masks.
60 duplicates, mostly face paints, pajamas and the only two glasses models.

Starred sniper rifle skin One of the starred weapon skins.

Starred weapon skin Another starred skin.

Starred weapon skin A third starred skin.

Starred weapon skin A fourth starred skin.

The face paints dropped over a hundred times in the author's run.

One of the common face paints.

Second 200 cases

Many legendary skins, sometimes in streaks.

65 weapon skins: 35 legendary, 22 regular and 9 starred.
135 character items: 17 pajamas, 18 masks (2 legendary), 44 face paints, 19 outfits (15 legendary), 8 hats (5 legendary) and a couple of glasses.

Third 200 cases

New skins still dropped in the fifth and sixth hundred, but face paints kept repeating.

70 weapon skins: 33 legendary (many new), 12 starred (only 4 variants exist) and 20 regular (only 4 or 5 variants).
130 character items: 26 hats (4 legendary, none new), 19 pajamas, 45 face paints (only 5 or 6 exist, so already over a hundred owned), 16 outfits (6 legendary, one new), 5 glasses (only 4 kinds) and 9 masks (4 legendary, none new).

Thoughts on the skins

The game has many weapon and character skins, but the author finds the legendary masks, hats and accessories ugly: they are plain solid gold, which makes the ordinary versions look better. Weapon skins, on the other hand, look great.

Legendary mask example A mask from the examples.

Legendary accessory example An accessory example.

Legendary accessory example Another accessory example.

Weapon skin example A weapon skin.

Weapon skin example Another weapon skin.

The author planned to add more numbers and possibly new skins over time.

FAQ

Can items from the free cases be sold?: According to the author, no. The cases drop often through normal play and their loot cannot be sold, so farming them has no market value.
What rarities do character items have?: Only two: rare and legendary. Weapon skins have more quality levels.
Which weapon skin qualities dropped?: Only three of the five: blue (regular), gold (legendary) and starred. Gold and starred skins have no wear gradation.