This Dobro model 33D resonator guitar, serial number B 446 8, belonged to the late Jaap van Kempen, one of my predecessor guitarists/bajoists of the Dutch Swing College Band. The widow of Jaap kindly let me have this Dobro when I bought the Vegaphone banjo.
Model 33D has a chrome plated bell brass body with beautiful “Swirl motive” engravings. The 33D is also (verbally) referred to as the “French Scroll” design, and/or the “Art Deco” design, and/or the “Art Nouveau” design. It has a singlecone resonator with biscuit bridge.
According to this website, the B in the serial number stands for Brass. #446 was made in 1971.
Bell brass is an alloy used for making bells and related instruments, such as cymbals. It is a form of bronze with a higher tin content, usually in approximately a 4:1 ratio of copper to tin (typically, 78% copper, 22% tin by mass). It is the combination of low internal damping and low internal sound velocity that makes bell metal specially suitable for resonant instruments.