Cover To Peru "Rebut" (Returned)

I can't read the message on the back. I assume it's the reason for the return.

Correo del Callao
Esta carta no ha sido reclamada, ni se conoce al destinatario

jorgesurcl has the transcription correct. My wife (who is originally from Ecuador) translates this as:

Mail from El Callao

This letter has not been claimed, nor is the recipient known

El Callao is the chief seaport in Peru, and was (and remains) a significant financial center.

(Also, really fantastic cover you've got there, stampcrow! I'm drooling over it. )

Ah hah, I knew I would get a translation here. Thank you!

I thought it might be expected to have a received stamp upon return to Wooster.

Correo del Callao can also be translated as either "Mail of Callao" or more loosely "Callao Post". I think that one of these alternate translations might be more accurate in this particular case since the marking seems to have been applied by the Callao post office to indicate no one had come to the post office to pick it up, and they did not know of anyone by that name in town to which they might try to deliver it.

Wish the contents were still with it.