1. How long have you been playing this game
2. How many coefficient 5 items you found so far
3. If any, which coefficient 5 items you never found
I'll start.

1. Playing for some months, maybe like 4?
2. So I have:
Green Beer Mushroom x2
Ace of Diamonds x2
Tuber's Bag x2
Green-Moss Pearl x1
Chourou's Hair x3
Book of Mushrooms x3
Book of Stars x2

Chocolate Mousse x3
Manda x1
Shallots x1
White Beans x1
Cauliflower x1
Almond Laxative x1
Meluzzine Key x1
3. I have yet to find:
Daruma Watermelon
Croissant
Octopus in Ink
Curly
Evil Liquor
Chaos Stapler