I have a few pieces with black inclusions similar in technique to this piece, but none are quite the same. It's a heavy (former) ashtray 978 g (2lbs 2 1/2 oz), and 16 cm long X 7 cm high (6 1/4" X 2 3/4"). The centre part of the bottom is a different technique from the the rest of piece. The crackled black seems to be result of a foil/leaf application. That section has no bubbles in it. The base is concave with a good bit of wear on the perimeter. It's not a masterpiece, but I think it's an good example of an interesting technique. One maker comes to mind, but I'd love to hear other ideas. Please!