Can I use your appraisal to sell my cards?
In short: You can use it to decide whether and how to sell, and you can show it to a buyer. I will not sell the cards for you, make an offer or negotiate on your behalf.
A sale decision is one of the purposes I appraise for. The report tells you what the cards are worth on a stated basis, which helps you set expectations before you list, consign or accept an offer somewhere else.
What I will not do is take any part in the sale itself. That separation is what keeps the opinion clean. A buyer can trust the report precisely because I gain nothing from the price.