This primary source comes from the Records of the Patent and Trademark Office.
National Archives Identifier:
4531663Full Citation: Drawing of Improvement in Projectiles for Rifled Ordnance; 8/20/1861; Records of the Patent and Trademark Office, Record Group 241. [Online Version, https://www.docsteach.org/documents/document/drawing-of-improvement-in-projectiles-for-rifled-ordnance, April 19, 2024]