The question is what to do when  IRS has never officially legitimized its position under Code Section 408(m), as to the definition of collectible. Their dicta in publications seems to be based on wishes and whims, not on the law.  

"Proposed regulations from 1984, never finalized, would have expanded collectibles to include any musical instrument, any historical object (documents, clothes, and so forth), and any other tangible property that the Treasury secretary determined to be a collectible, presumably after an appropriate amount of notice and comment under the Administrative Procedure Act. The proposed regulations would have applied to property acquired in 1982 or later."

From an interesting article at

https://www.friedfrank.com/uploads/siteFiles/Publications/Zhang_TN_Taxation%20of%20Collectibles.pdf