Small Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 1.9
Communication Breakdown; Training / Qualification
ATC Issue All Types; Airspace Violation All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert
Airspace Structure; Procedure
I was providing OJT on Local Control 2. Aircraft X was an IFR departure. The aircraft was given the incorrect Departure frequency. Upon shipping aircraft; the trainee realized it should have been Diablo frequency and that a departure release was required. She gave Aircraft X the correct frequency and then called Diablo to ask for release but aircraft was already airborne. We should have had a CFR placard displayed as a visual cue to call Diablo for release.
OAK Tower Local Controller; realizes aircraft departed airport without a release.  Memory jogger was not used.