the Nimrud lens — Assyrian telescope or just a fire-starter, why is this still unsettled

Found by Layard in 1850 at Nimrud, Iraq. Rock crystal, ground and polished into an asymmetric lens shape. 7th century BCE. Sir David Brewster catalogued it in 1853 and proposed it was part of an optical instrument. Most archaeologists say fire-lighting tool or decorative piece. But the grinding is w……