What could this object be?

![](https://steemitimages.com/DQmRfJ2wPg8VtL2psRatMA8ZZ8dMSUjcKoscVFm87pCZP3Y/image.png)

It is small enough to be hidden easily. It is hollow and capped. It has a magnetic bottom.

Can you guess what this is?


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*Photo © 2017 by @ervin-lemark*
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