To be used when a situation seems smelly, but you are sure it is indeed OK. Can be used in similar situations that the phrase "Catch 22" is used.
Two guys are at a flea market, and find a sweet bicycle, but its so nice, it looks almost stolen. A kid is selling it, and he offers it to them for 50 bucks, when it would normally cost $100.00+. Guy 1 turns to guy two, "Yo man, what do you think about this deal?" Guy two, answers reassuringly, knowing that this is a legit sale, "Ionno, its seems a bit sketch, but its prolly Ranch 99."