: In the 19th century, certain dictionaries—such as The Slang Dictionary —were offered in special editions interleaved with finely-ruled paper . These blank pages were specifically intended for the "asseverator" or collector of new words to record slang and colloquial terms as they emerged.
While it is not a standard term for a specific type of paper, its appearance in the context of "paper" typically relates to its historical use in and specialized dictionary publishing : asseverator
If you are looking for a specific industrial or commercial paper brand by this name, it does not appear to be a widely recognized product in the modern paper manufacturing industry. Asseveration - The Free Dictionary : In the 19th century, certain dictionaries—such as