The No. 18203 is the coarse replacement blade for the Z-Saw Tuck-In 240 Coarse (No. 18003), the folding saw for pruning and green wood.
It's the same 240 mm (9.4 in) blade the Coarse saw comes with: 1.0 mm thick with big teeth at a 3.2 mm pitch (8 TPI) and a 1.28 mm kerf. It's a pin-fit blade, so when the teeth dull you swap the blade and keep the 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.