TRAINEE APCH CTLR DESCENDED AN SMT THROUGH ALT OF ENROUTE MDT. ACFT INITIALLY UNDER SEPARATE ATC JURISDICTION. LESS THAN STANDARD SEPARATION DETECTED BY ARTCC OEDP AND APCH CTLR ADVISED.

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I WAS INSTRUCTING A TRNEE WORKING THE RADAR FLT POS. MDT Y WAS AN OVERFLT AT 9000' SBND ON V23 ABOUT OVER ALBANY; OR. SMT X WAS SBND FOR LNDG AT EUG. ALT WAS DSNDING FROM 10400 TO 10000' ON INITIAL CONTACT. SMT X WAS APPROX 2 MI E OF MDT Y. THE RADAR CTLR ON HER FIRST XMISSION GAVE SMT X DSCNT TO 5000'. SHE QUICKLY SAW A CONFLICT POSSIBILITY AND CALLED THE SEA CENTER SECTOR FOR CTL OF MDT Y. SHE ISSUED A RIGHT TURN HDG 210 DEGS TO MDT Y; BUT ALT READOUT TO ME SHOWED MDT Y AT 9100' AND SMT X AT 9800'. SHORTLY A CALL CAME TO THE SUPVR'S DESK WHICH I TOLD MY TRNEE TO ANSWER. IT WAS THE SEA CENTER SUPVR WITH A RPT THAT THE 2 ACFT WERE 2 MI APART AS SHOWN ON THEIR ALARM SYS W/O A THOUSAND FT VERT SEP IN THE CLOUDS. A BRIEF INVESTIGATION AND REPLAY OF THE TAPED VOICE RECORDING FOLLOWED. THE OCCURRENCE WAS DISMISSED WITH NO FURTHER REQUEST FOR DATA PRINTOUT FROM THE SEA CENTER COMPUTER. PLANES INVOLVED WERE IN CLOUDS AND SO NO VISUAL SIGHTING OCCURRED OF EACH OTHER. VERY POOR CTLR JUDGEMENT IN AN OBVIOUS SITUATION. 1000' AND 3 MI SEP VERY DOUBTFUL! PREVENTION: DON'T DO IT AGAIN.