Most LOGAN straight mountcutters use the #270 blade. It is identified by the oval hole.
The Logan #271 blade is the same size and thickness as the #270. The difference is that #271 has a single bevel, being ground on one side only. We call it an SE blade. Some framers find that an SE blade cuts thicker and tougher boards such as cotton rag better.
#271 blades fit the 5000 8 Ply hand cutter (Part no. 7022). To fit, the side with the ground edge faces you when looking at the side face of the 5000. In other words, the sharp edge faces out from the cutter.