To determine the year of manufacture for a Springfield shotgun with serial number 51089, you would typically need to reference the specific production records or a serial number lookup chart for the model in question, as Springfield produced various shotguns over the years. Generally, Springfield shotguns were manufactured primarily in the early to mid-20th century. If you have additional information about the model, that could help narrow it down further. For precise dating, consulting a firearm historian or reference guide would be advisable.