These dear little gems get their name as a short version of "artists cards editions and originals".
Their natural home seems to be online and all sort of sites, eBay and Etsy particularly have loads and loads of examples.
|Mary Kemp - Stonehenge - Pair of ACEOs.|
I've just sold these two of Stonehenge from my Etsy Shop, Florence Fantasy Art.
I shall have to paint some more. They're enormous fun.