On a new stainless steel spoon if you see the image of your face upside down, then that part of the spoon acts like,
Concave mirror forms the inverted image of an object, therefore the portion of the spoon in which our face is upside down is a concave mirror. A convex mirror always forms the erect and virtual image. And since the spoon is not transparent hence it is not any type of lens.
The figure below illustrates the situation.

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