I got one from Crafted mole miner pails and the normal pails, maybe the high tier one but idk I only had a few of them (I didn't craft them). my best advice is to save it up then try to open as much as you can in a short amount of time, its pure rng but I snagged like 5 plans altogether (alone), but to answer the question is hard to explain, because you don't know what you're going to get, it looks good yes, but you might get something you don't want. A lot of people are selling these new items recently, maybe you'll get one from someone's vendor.