On auction:  The Centennial Postage Dues (aka "Red Dues"):  "Second Issue".  This is the most valuable of the four "Red Dues" issued.  The book value of the Second Issue is $23.35.  The stamps are superb:  fresh, bright, well centred and mint never hinged.

I combine shipping:  After the first purchase, I add 50c to each additional purchase if completed within a week of the first purchase.  After you have completed your purchases, ask the seller to send you a combined shipping invoice to substantially reduce your shipping cost.  Make sure to pay the seller’s combined shipping invoice to receive the shipping discount.  Do not pay the automated eBay invoice which does not reduce the shipping cost.