The No. 07124 is the replacement blade for the Z-Saw Hardwood Dozuki 240 (No. 07123), the Japanese back saw for fine joinery in hardwood: dovetails, tenons and furniture restoration.
It's the same 240 mm (9.45 in) blade the saw comes with: 0.30 mm thick, with impulse-hardened teeth at a 1.2 mm pitch (21 TPI) that cut both with and across the grain. It's a hook-fit blade: to change it, wrap the blade in a rag, hold the saw upside down by the blade and tap the handle on a firm surface, then fit the new blade and keep your handle.
Z-Saw's maker, Okada Hardware, has made saws in Miki, Japan since 1943 and was the first company in Japan to impulse-harden saw teeth.