Peru 1930s registration plate, what is the meaning of the lettering?

Mar 2017
The Netherlands
Ola amigos,
Can you please help me find the meaning of the lettering on this late 1920s, early 1930s Peru, thought to be for official use. The lettering contains a C, a P and an M (probably). Do you have an idea what this could mean? Does anyone have a photograph with a vehicle from that era?
Best regards,