Aside from the obvious that it is a portable grate, these items don't usually have top grates. I would think this one could have been used to heat sad irons, or even as a cooking surface.
Prices on these can vary significantly. It all really depends on condition, which is difficult to determine when given one photo of an unrestored grate. Cracks, breaks, and pitting will affect the price significantly. This piece is also rather small when compared to other portable grates I have seen.
Honestly, I would give as little as possible for this piece; because, I know from experience how difficult these pieces are to clean.
Check out this link if you would like to see some photos and read about a restoration:
http://www.griswoldandwagner.com/cgi-bin/yabb/YaBB.pl?num=1509713493/0#0
