As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BWI - FLT 2539 - ABOUT 50 MILES OUT OF BWI, THE CREW OBSERVED ZERO OIL PRESSURE ON THE NR 1 ENGINE. ALL OTHER INDICATIONS WERE NORMAL. FLIGHT RETURNED TO FIELD AT BWI. THE ENGINE WAS NOT SHUT DOWN AND NO EMERGENCY EQUIPMENT WAS CALLED OUT. THE FLIGHT LANDED WITH NO FURTHER INCIDENT. MAINTENANCE REPLACED THE NR 1 ENGINE OIL PRESSURE INDICATOR. (X)