robin egg blue

a robin's egg and some old govt correspondence
Michael Carrithers commented that b&w photos of rust are not entirely informative. I am taking his words as an invitation.
Despite my monochromatic preference (“friends don’t let friends shoot colour”), I am falling off the wagon for a few days, into the chaos and mess, 390 to 750 nanometers.
Blue egg of Robin largely meaningless in b&w would be.