@rabbijill Previous owner must have had one of those fancy wood-fired microwaves 😁
Depending on the size, could be chickadees. https://happyacres.blog/2015/04/15/nesting-chickadees/
My first thought was gecko eggs too. They are notorious for laying eggs in every nook and cranny.
I suppose you would find them in other places too though so maybe some sort of bird?
@rabbijill Could be gecko. This page (lots of weird ads) has a chart of gecko egg sizes:
https://www.reptilehero.com/what-gecko-eggs-look-like-size-color/