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dgpretzel wrote:Why would a BBb tuba be called a baritone tuba? (I thought a BBb tuba was referred to as a contrabass tuba)

It wouldn't, and you are correct that the Bb tuba is a contrabass.

The eBay listing you linked doesn't call the horn for sale a "baritone tuba." The category it's listed in is merely "Baritones and Tubas" which is shortened in the Product Type as "Baritone, Tuba."

not everyone who posts on eBay knows what they are talking about, either.