Crest or Non Crest Share certificate?

This is probably a silly question but this is my first time trying to sell some shares. I have opened an account with an online share dealing service and I have a share certificate to send them so that they can sell the shares for me. There is a choice of two forms to complete, CREST or non CREST.

Is there something on the share certificate which will tell me which it is? I have just received the certificate and it is for shares in a single PLC.