Hi Nicki, I sent the coins for grading and conservation in the non-pvc flips. Made sure that bubble wrap would prevent them moving around and put this in a bubble wrap envelope that was made immobile by bubble wrap in a sturdy sealed box.
Let's hope it works. The form mentioned to add as much info about the coins as possible, so apart from the obvious I added the original bill from the auction place where my father bought the coin set in 1979. Plus pictures of the original set box and the coins while they were in the box. I did not send the box itself, since it does not provide any protection during shipping.
I am looking forward to the grading process. If this works well I do have more coins that deserve grading and conservation care.
Thanks for your and Kailee's help!