13....Not enough is known about this artist (by the author) to justify a rating.
14....This artist's original works may have regional, historical value.
15....According to the number and quality of references this artist's original works appear to be quite collectible and valuable.
16....According to the number and quality of references this artist's original works appear to be collectible and relatively valuable.
17....According to the number and quality of references this artist's original works appear to be collectible and have potential value.
18....According to the number and quality of references this artist's original works appear to be quite collectible and extremely valuable.