It is not actually a dutch oven. You have a kettle. Commonly called a bean pot . The gatemark places the pot in a wide range of dates. I see a 8 and a foundry mark, the N. The 8 is a common size, the mark could be a pourer (the person that poured the metal) to account for the number or casts they made. A safe easy date is pre 1920's. The cowhorn ears push it back to the 1890's. Perhaps a few years earlier. If the ears were flat on the top and thicker the date could go back to the 1820's - 1840's. With no records the history is vague. Hope this helps, if not ignore it.
"Where are all the spider skillet lids??"