The part number 4438091 (or 4438-091) corresponds to a Harley-Davidson License Plate Bracket / Rear Fender Component typically found on Sportster models. 
Product Specifications & Fitment
  • Primary Component: This stamp number is widely associated with the inner structural mounting bracket or base plate assembly for the rear license plate and reflector area. 
  • Compatible Models:
    • Harley-Davidson Sportster Forty-Eight (XL1200X)
    • Harley-Davidson Sportster Iron 883 (XL883N) 
  • Material & Construction: Usually manufactured from robust black-finished steel or aluminum to securely bolt underneath or onto the rear fender setup.