If "052971" is a tracking number, internal code, or international code, it would not appear in US domestic postal records. To get you the specific details you need, could you:
An area in Indian River County.
(e.g., a city name, a county, or a location for shipping)? Introduction of the ZIP Code - U.S. Postal Facts 052971 zip
A "unique" ZIP code, which usually applies to a single large building, company, or institution. Understanding 5-Digit ZIP Codes (00000-99999) If "052971" is a tracking number, internal code,