the one time i went and bought a bunch of keys, (about 25 from the store for a mass unboxing), they didn't have an untradeable marker, i think if your purchase price goes higher than a certain amount they become tradeable immediately
Pretty pretty is the horsey who hath drunken the magic tequila
I think that if you made your first purchase before a certain point then all items you buy are instantly tradable and items unboxed are tradable also. If you didn't make a purchase before that point then its untradable for a few days.
XBL=Inspired Arts PSN=ULT1MATESPARTAN Arto-po-stat-alo