Used 52mm ID Lens Cap Made in Japan B00601

Unknown brand cap. Not sure what lens it might fit. Inner diameter is 52.3mm. 
Outer OD is 56.6mm. And it is 20.3mm deep.

But it is not damaged in any way, no cracks or dents. This cap is fully operational and functions as intended.  I would rate it an 8, on a scale from 1 to 10.