Your US Navy uniform button, having an oval shield on the button's right, is from the War-of-1812 Era, definitely not pre-1800. (That info is from the button-book by Alphaeus H. Albert.)
Additional info from the Albert button-book:
If a US Navy "anchor-in-a-shield" button has stars encircling the main emblem, it is from 1802 to "approximately" 1820. If it doesn't have the stars, it is from 1798 into early-1802.