The 389-24 is the Kataba Extra Fine replacement blade for the Silky Woodboy 240, the Japanese folding pull saw for fine woodworking and joinery. It's the blade that comes on the Woodboy Kataba Extra Fine (388-24), and it fits any Woodboy 240 handle.
It's 240 mm (9-1/2 in) long and 0.65 mm thick, backless, with 32 teeth per 30 mm (about 27 TPI), for smooth, fine cuts. The teeth are non-set and the chrome-plated blade is taper ground, so it cuts a clean, narrow kerf. When the teeth dull, fit a new blade and keep your handle.
Katsuji Miyawaki founded Silky in 1919 in Kishi, Japan, under the brand Tamakitsune, and all of its saws took the Silky name in 1983. The company is now headed by Uichi Miyawaki, and its saws are made in Ono, Japan.