These saws are easy to use for pruning fruit trees.  The sizes S, M and L indicate the TPI (teeth per inch) for each saw.  The small size would have smaller space between each tooth, and the large would have bigger gaps.  The small size would make smoother cuts, whereas the larger size would offer a quicker cut, but rough cuts compared to the small and medium.  

Brand: Nakaya
Producing Area: Sanjo City / Japan 
Profile: Pruning Saw for Fruit Trees
Blade Size: 279mm 
Edge Length: 270mm 
Handle Length: 145mm
Total Length:424mm
Steel: SK85