Well, with a last name that is a common word otherwise (Fortune), and no date, and not even knowing if this came from the California "gallery" or the one in Illinois, searches are going to take more time than I can afford right now.
Telephone area codes and postal zip codes change a lot in California, as the population grows, so you might get a date range by researching one or both.
I will tell you that if you do a search on eBay and other on-line venues, you'll find that these Robert Sills Gallery pieces are usually offered in the $25 to $50 range -- although there are, of course, exceptions.
Sorry not to be of more help. If ARGON comes along, he'll nail it in no time. 
So others can see it better:
@maxine*j wrote:
If ARGON comes along, he'll nail it in no time.
Haha, just trying to put me on the spot 
I have nothing to offer on this, except to say that in an eBay listing I don't think knowing the first name would make much difference. In the unlikely event that buyers happen to be looking for this specific artist they will find the listing in any case, using "Fortune" as the keyword. Even if further details on the artist could be found, I doubt they would have any impact upon a sale.
