ATR 42
Air Traffic Control Fully Certified
Communication Breakdown; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance
Staffing; Human Factors
Working three sectors combined; I had a D-Side. An ATR42 inbound to ADQ descending to 060. A Fairchild SA-227 Metro was released (rather late) climbing to the MIA of 050. The ATR42 had the airport in sight; had requested clearance for the visual approach; was told to continue inbound and advised of the Metro traffic climbing to 050. I knew he was getting close to the airport; I had traffic complexity issues at 3 different airports going on at the same time. I was thinking one thing but my mouth was saying something different as my brain started moving on to the next task.  I requested the ATR42 report 5 miles north of the VOR and decided I had better give him a holding clearance just in case (though didn't expect he would hold) in my holding clearance I told him to maintain 050 instead of 060. I didn't realize I had said it; he even read back 050 and I didn't hear the read back. Listening to the tape you could hear the hesitancy so I believe he was questioning it but he didn't say anything. Fortunately my D-Side looked at me funny and the Supervisor who had been monitoring looked at me funny and said; 'You know you said 050 right?' I didn't know it; but I didn't waste any time fixing it. Both aircraft were non RADAR; however the Metro had just reported 040 and I believe the ATR42 was barely out of 070 so I do not believe separation was actually lost but I did not only give an altitude I didn't intend; but also missed the read back. Teamwork saved this; my D-Side as well as the Supervisor monitoring the busy session. Staffing staffing staffing. Our staffing is hurting so badly; Sector 9 should have been split off long before the incident but we are so tight that we push the traffic volumes. Expectancy factor and moving on to the next task bit me.  Secondly; having a Supervisor monitoring; being that extra pair of ears paid off here. All too often at our facility; we have supervisors working our area that are neither assigned to our area nor certified in any sector in our area. The have zero knowledge of the sectors within that area and are unable to provide the type of assistance that this particular Supervisor was able to provide. This one happened to be assigned to the area and certified on a couple of sectors within the area.
ZAN Controller described a near loss of separation when intending to issue one altitude but in fact issued another caught by a fellow controller and corrected.