Ha! Finally! Here it is with a Three Dog Bakery cookie for scale (because even though it's a dog treat, I figure everyone knows how big an Oreo is):
I have a sneaking suspicion that this well-formed specimen is not actually the very first duck egg. Recently, a certain Rouen female has been spending an undue amount of time underneath the chicken house. I will add "Block Access to Crawl Space" to my list of things to do.