This is an absolutely rare black Seto chawan ( setoguro chawan ) from the late Momoyama Period, which means the late 16th century or the changeover from Azuchi Momoyama to early Edo.
Blackish-brown glaze amalgamates with a wild and roughly thrown body. It is very heavy for a tea bowl, almost 500g. Please note that there is also an interesting kiln mark ( watch image number 3 )
Setoguro yaki is high-fired ware that originated in the late 16th century. Black glaze is achieved by removing the iron-glazed pots from the kiln when they are red-hot (a technique called hikidashi guro).
Great condition - no damages, no cracks except inborn kiln cracks
Size: 8,5 in height x 13 cm in diameter