This is a replacement MC key for W4 caravan locks. The key can be cut from the key code or a decent picture of an existing key.
The key code will take one of the following formats:
- The letters MC followed by a number in the range of 01 to 40
- The letters MW followed by a number in the range of 1 to 279
- The letter X followed by a number in the range of 1 to 100
The key code is usually stamped on the face of the lock.
Alternatively... the key can be cut from a decent digital picture of an existing key.
A picture like this taken from the top:

The new key will be stamped with the key code.