ACR HAS NMAC WITH SMA.

Narrative

FLYING A 727 WE WERE LEVEL AT 3000 FT 15 MI FROM THE ARPT. THEY CLRED US DOWN TO 1700 FT IN PREPARATION FOR THE 'LAGOON VISUAL APCH.' WHICH WE HAVE ALWAYS THOUGHT WAS A 'PROTECTED ALT OVER THE SMALLER ARPT 6 MI TO THE W OF THE SJU ARPT. THEY ARE RESTR TO 1200 FT. AS WE WERE ALMOST 10-11 MI OUT ON A 'DOG-LEG' TO FINAL; WE ADVISED WE HAD THE ARPT IN SIGHT. HE ADVISED US TO 'MAINTAIN 1700 FT UNTIL INTERCEPTING THE LAGOON VISUAL APCH. CLRED FOR THE LAGOON VISUAL; CONTACT THE TWR 118.3;' WHILE WE DID. CONTINUING DOWN THROUGH 300 FT; I HAPPENED TO LOOK AT THE TCASII AND NOTICED AN ACFT 11:30 TO 12 O'CLOCK 3 MI AT 200 FT WHICH AT THE SAME TIME THE TCASII SAID 'TFC; TFC.' I ADVISED THE FO I HAD THE ACFT (WE WERE AT 2100 FT AT THIS TIME). I RECEIVED A RA 'MONITOR VERT SPD THROUGH CLB;' WHICH I HAD ALREADY CLRED. WE WERE AT 2400 FT WHEN A COMANCHE WENT UNDER US AT ABOUT 2000 FT. WE WERE IN THE PROCESS OF SWITCHING TO TWR WHEN THIS HAPPENED; AND ADVISED THE TWR WE WERE IN CLB BECAUSE OF A TCASII ADVISORY. HE ADVISED US TO CALL THE TWR ON THE GND; WHICH WE DID. THEY HAD APPARENTLY CLRED THE ACFT ON A DEP AND WAS CLRED TO 2000 FT ON THE DEP. HOWEVER; I FOUND OUT LATER THAT THE ACFT WAS NORMALLY LIMITED TO 1200 FT AT THAT SATELLITE ARPT. CLOSE CALL. TCASII DID A GOOD JOB.