I foresaw provenance being a big deal with crypto coins.
1. I have all of the correspondence with any deal I've made on this forum and others.
2. I have most of the envelopes / boxes the coins were shipped to me in.
3. I recorded on the box The Forum member I purchased the coins from, the coins, the serial number of the coins, the amount I paid in Bitcoin and translated into u.s. dollars.
4. And most importantly I left feedback with the reference to the original listing of where I purchased them.
I'm thinking about putting a list of the coins I own on this forum with all the details on the coin such as a description of the coin, funded or unfunded, who I bought the coins from with reference link if applicable, the date purchased, and pictures of the coins and COA's and such. All this to prove provenance and the validity of my collection.
that is a nice idea indeed but you would also be showing your assets which might bring fud and risk to you!
I guess as long you have the details of your purchase, it should be fine when it comes to selling them