The 291-24 is the fine-tooth replacement blade for the Silky Gomboy 240 folding saw, for cleaner cuts in dry wood than the medium blade the saw comes with.
It's 240 mm (9.45 in) long, with fine teeth at 14 per 30 mm (about 12 TPI). Fit it on the saw's pivot screw in place of the medium blade, and keep the medium for limbing and green wood.
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.