I may be restating the obvious but in case I'm not, to be explicit you already put it in backwards thus could have killed either the driver, the laser diode (LD), or both. You'll have to separately test each to find out. Make sure you have current control when testing the LD or you'll have yet another chance to damage the LD.
And to make matters worse, I just tested a laser driver (SXD V3) using a resistor load instead of a diode test load. Readings were so crazy I stopped and bought a 20A laser test load from Survival Laser. Now the test load is fried and I'm kinda wondering if I blew it with a damaged driver, all started by not using a diode test load in the first place (D1 measures OK, D2-D8 are shorted in both directions?!). We'll see if Survival replaces it after testing it themselves.
And to your spring comment, more of my lasers than not have springs on both ends. I also thought it was a matter of simply matching battery-negative with the spring so each time I get another laser, I'm left scrambling to ask the seller or find documentation.
