When Betty saw the scales, her eyes opened wide, and her ears twitched. She had never seen that scale before, but could at a glance tell who it belonged to. That was one of Luminous's scales. She had an inkling about where it came from.
When Luminous retired from the war and came back to the mortal world, she was severely injured and had to recover. She was also trying to get rid of her radiant light. The first method she tried was shedding all of her scales. One by one, Luminous tore all of her scales off in an attempt to put a stop to her light.
Those scales she tore off and threw away; this must be one of them. How did it end up here with the apes? Betty herself has no idea. But, it could've been picked by some dragon in the past, then ended up collected by the apes when they raided their hoard.
