Mystery Theme VI: Topic Occluded by KlionskyG

Question 2

Until English engineer Edward Nairne developed a prototype of this common item, people used wax, pumice, or sandstone -- or crustless bread -- to do the job. Joseph Priestley may have given this item some oxygen within the first few months when he wrote, "I have seen a substance excellently adapted to the purpose of [redacted] ... It is sold by Mr. Nairne, Mathematical Instrument-Maker".

What item did Nairne invent?

(rubber) eraser (invention date unknown; Priestley's quote is from April 15, 1770)