I would agree with David regarding the materials of the kinatah, I apparently see some traces of "vert de gris" (green copper compound) on the reverse side of the blade, which should indicate that the kinatah is from brass (may be gilt).
Regarding the estimated age of the piece, the seller just says that it was brought to the US after WW2 but this is not a very accurate statement
From the pictures and if it was my decision I would categorize the kris as probably from tangguh kamardikan muda Madura but of course I can prove wrong and the piece is quite well made.
The seller also proposes another kris with a kinatah blade of similar quality.
Regards