eBay remains the best source of estimates of current values, by examining "sold" listings vs. asking prices or simply "completed" listings. Among Griswold DOs, those with the "full writing top" covers are more desirable. Small DOs like the #6 often command higher prices than the relatively more common #8s, and can run into the hundreds of dollars. Or you can get lucky and find one spray painted black at a flea market for $21 like I did. Of course, condition is everything, so pitting from rust, warped bottoms and cracks in the sides all detract from value, often sharply.