This means the above 3 colletion weapons CANNOT be found through regular item-drop system
Souvenir Packages
There are sometimes tournaments that come around that Valve designs Souvenir packages for. By linking your CS:GO account to a Twitch account or GOTV account, you can watch matches and have a chance to receive a Souvenir Package after a match ends
It doesn't matter if you've paid for a ton of skins for the game or never spent a cent on the game, you can get Souvenir packages regardless.
Graffiti
Valve released a new update to CS:GO. It include graffiti/spray as well as other fixes. Most of them are Paid Sprays.
However, you can still get a basic spray as an item drop.
You can receive one weapon drop per week. You will receive this drop the first time you increase your Rank during the week. Your level progress bar will indicate when you are eligible for an earned weapon. so the more you play, there will be more chance to get random drops but you will sure get one weapon drop per week when you will increase your rank.
Best Answer
Skill Ranks
You get drops on all ranks.
Profile Levels
You get drops on levelup, on every levelup, limited to once every week.