Is 12-month standard OPT a different visa?
No. A student with 12-month standard OPT authorization is an F-1 student holding an EAD for OPT. You still need an OISS advisor signature on your I-20 if you want to re-enter the United States during your time on 12-month standard OPT. The OISS advisor signature should be no more than six months old at the time you re-enter.