Over Berwick-upon-Tweed, Northumberland, UK.

A high Stratocumulus cloud layer like this can be hard to distinguish from a low Altocumulus one. It is Stratocumulus when the base of the cloud layer is lower than 6,500ft (this altitude applies to mid-latitude regions of the world).

Full classification:

Other examples of Stratocumulus:
Over The Marmolada, Italy.

Stratocumulus stratiformis

On a flight from Hanoi to Kuala Lumpur.

Stratocumulus castellanus