A saw like that is probably made out of some kind of spring steel, maybe 1075 or 5160.

The teeth were probably originally cut when the saw blade was in an annealed state. It's going to be very difficult to cut now that it's been heat treated. I would probably use a rotary tool with a diamond cutting wheel. But you can get diamond blades for your hacksaw. Here's an example: https://www.amazon.com/C-R-Laurence-Diamond-Wire-Blade/dp/B006JFNOSK