"Payment must be made within 3 business days" - This is a bit short. We actually don't state a time frame and rarely have problems (if the bidder is intending to pay

). If you want to state a time frame, I'd make it 7 or 10 days to allow a little breathing room to get a money order and get it mailed. I would also change "made" to "received".
I would suggest changing your shipping method to First Class. There's not that much of a difference and, even in a bubble mailer, you can ship multiple coins and still stay under 2 oz. If you do your postage online, you can save yourself a lot on the DC. It's only 18 cents. Since you are accepting Paypal, be sure to only ship to Confirmed US addresses and use Delivery Confirmation on every package worth under $250. Anything over $250, use signature confirmation. If you don't, you will not be covered under Paypal's Seller Protection.
You may as well remove the "I am not responsible for lost or damaged items" sentence. Regardless of whether someone purchases insurance or not, the seller is 100% responsible to get the item to the buyer or to promptly refund their money. That's why mail order companies always include insurance in their postage price. That sentence will not get you off the hook if there is a problem. For this reason, you may want to insure items that are worth more even if the customer has not paid for it. Insurance is actually protection for you, not the buyer.
I would state that the coin must be in the original, untampered holder or the guarantee is void. This will protect you from buyers switching coins on you, though in all the years we've been selling, we've never had a problem with that.
I would also suggest providing pictures of both sides of the coin. If you build your auctions in a WYSIWYG editor, you can insert the pictures right into the auction itself and not have to pay
ebay for hosting. This also gives you the advantage of being able to use as many pics as you want at no charge. You can always host your pics here in your gallery and link to them.
ebay compresses their images, so your pictures will be nicer this way, also.
You are welcome to borrow any wording from our auctions if you like. Just click on the Our Coins For Sale link in my signature and you can see our auctions. Please feel free to email me if there is anything else I can do to help.
