If they're red Craftsman versions of 3400's then they're 3.4's. Red 3.7's are usually 3700's, but a few late ones were 3800's. Grey 3.7's are all 3800s. I'd like to find a nice 3.7 labeled 3700......
I just checked. The red Craftsman says 3.7 18 and the gray one doesn't say anything but they have the same Craftsman model number 358.356091. I'm writing this number by memory, should have written it down instead. The gray one always seemed peppier than the red one, maybe it's because the red one is smaller.