If you have a digital postal scale or anything that weighs in 10th of ounces you can weigh your eggs easily.
In the USA, a large egg weighs 2.0-2.2 ounces. Extra Large is 2.3-2.4 ounces. Jumbo is heavier than 2.4. Medium is less than 2.0 ounces, but I don't remember the bottom end of "medium" because all the eggs my girls lay are 2.0 ounces and more.
Turn it on, put a little dish on the weighing plate, hit "Tare" or "Zero" and then you can accurately weigh the egg. I write the date and M, L, XL, or J on the end in pencil.
There's a good article on Wikipedia about eggs and has the weight scales for several different countries. Canada, Australia, the UK and other countries use different cut off points for the different sizes, and they may be called different titles too.
The article also explains the varying degrees in grades of eggs.
As for washing... if I was purchasing eggs from a local seller I would be unhappy if they had bits of anything stuck to them, no matter what the grower said. Yes, they keep longer unwashed and unrefrigerated. But the gut reaction of 99% of purchasers in the USA would be "Yuck!, it's dirty and full of poo!!" and that would be the last I'd see that customer.
I could explain over and over and over that hardly any other country washes or refrigerates store bought eggs, but that's not going to change Ms. Average American Housewife's instinct. If someone is constantly washing everything with hand sanitizer and spraying her counters with bleach, do you think she'll accept unwashed, dirty looking eggs even if she mentally can accept they're fine? (Btw, I hate how hand sanitizer feels, and I just use plain hot soapy water on my countertops).
I do realize others have different opinions on washing and/or refrigerating eggs. I just go with what my customers want.