I just got through watching an episode of "Antiques Roadshow".
Season 25 Episode 3 "Vintage Baltimore Air 2021 Hour 2" Air Date 1/18/21
A woman found one like yours with the March date. It was in good shape because she found it in an old building, not in the ground. The auction expert told her that the button was made for Washington's March Inaugural but Washington wasn't inaugurated until April of that year because it was delayed so that more people could have time to travel to see the inauguration. At the end of the appraisal, (done in 2007) the expert told her it was worth about $3,000 @ auction. The 2021
price had increased to $5,000. For you & those interested, it would be worth it to watch that episode if you can find it on demand on the PBS site.
Congrats on your great find "Delmarva" !!!!!