While I've seen OOP used as "out of print", but used inaccurately (i.e. RARE OOP DARK ELF ASSASSIN - you mean the one that I saw on the shelf at GW yesterday?), I've never heard of it to mean "out of package". While it's unfortunate that the two phrases can be made into the same acronym, if you have something out of the package, then that should be spelled out along with its condition ("loose", should be a sufficiently succinct adjective).
For NIB/MIB, they've always referred to the condition of the item, not its edition. I've always considered them interchangeable, except with a very slight difference that would only matter to collectors; "new" indicates the item is sealed, shrink-wrapped, etc but may have some damage, while "mint" indicates not only that the item is sealed but that over all is in perfect condition, for the discerning collector.
The important thing to remember here is that miniatures don't generally identify their age by their name. So, if I have "Marneus Calgar NIB", you would want to ask which one it was. If I listed either "Classic Marneus Calgar NIB" or "Marneus Calgar with Honor Guard NIB" you would know exactly which it was.
However, things like M:tG cards identify themselves. A box of 3rd ed booster packs NIB is 3rd ed booster packs. A box of Arabian Nights or Zendikar boosters NIB clearly indicates exactly what you're getting. There is no "oops, I thought you meant 1st edition Zendikar, not 4th edition Zendikar" because there hasn't been multiple editions of the same thing. If you were trading for a Magic card that appeared in multiple editions, you would indicate which edition your card came from.
What do we learn from this? Clearly describe what you have. If it's a "NIB Space Marine Captain" tell us if it's the multipart plastic kit or one of the many in a blister. If he's in a blister, tell us his pose and equipment.
Just my 2 cents.
Location: Cincinnati, OH, USA
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