Hey Elveez,
if you sent the watch to Bienne for the restoration, AFAIK, you don't have to worry about the certificate as it will come back with that anyway. If not, or I was wrong, let me paste a quote here I received from Mr John Diethelm:
"
The A4 format certificate issued by our Customer Service is a document which shows all available details about ech watch. Such certificate will be issued and invoiced through our Customer Service in Bienne .
Best regards
John R. Diethelm