Artist Proofs are perhaps the most valued of his collection because he did more on each one than just a signature. He enhances the canvas with oil paints just like someone at the studio does for the signed and numbered canvas, but he adds to it his own style. When you buy an artist proof paper, he does a unique pencil sketch called a "remarque" that is also signed. The Remarque is usually in the lower left corner of the reproduction. AP's typically runs in shorter runs to keep with tradition.
Signed and Numbered
Signed and Numbered are created just as the artist proof, but the canvas is enhanced by an employee at Byerley Studio. SN's runs in larger runs and his collection, 500 canvas, and 1500 paper reproductions are the highest numbers that have been included in any edition. The SN paper does not have the Remarque, or the knocked out area for the sketch.
Open editions mean that they are unlimited reproductions. This would include but is not limited to posters on paper and canvas. In some cases, products are licensed and could include similar products such as posters but also include mugs, music boxes, and puzzles.