This is a Nanban style tsuba featuring a tessen karakusa (clematis arabesque) openwork design. It is made of iron with nikubori-jisukashi (carved openwork) and kin-nunomezogan (gold overlay inlay). The tsuba has a kawarigata (irregular) shape and kakumimi-koniku (square rim with slight flesh).

Iron-tsuba
A Hozon-certified fitting of notably superior craftsmanship and condition, often with signature or workmanship of high reference value.
The NBTHK (Nihon Bijutsu Tōken Hozon Kyōkai, the Society for the Preservation of Japanese Art Swords) is a public-interest incorporated foundation founded in 1948 and supervised by Japan’s Agency for Cultural Affairs (Bunkachō); it is based at the Japanese Sword Museum in Tokyo. Its expert panels physically examine each submitted work (shinsa) and issue a certificate (kanteishō) ranking it by artistic and historical merit. NBTHK papers are the most widely recognized standard of authentication for Japanese swords and fittings.
NBTHK official siteReturns/exchanges/cancellations not accepted after shipment except for significant defects; if defective, return/exchange possible within 3 days of arrival (return shipping paid by customer).