I never seen thermostat like this before !?

I have no idea what kind of the removed thermostat you had.. When flushing the cooling system, we removed the thermostat. There is no testing/ flushing thermostat that I know of..

You're installed the corrected thermostat. The thermostat (180F) for the D15Z1 start to open between 176F-183F and fully open at 203F.

Racing thermostats are looking like these:

http://www.mishimoto.com/honda-racing-thermostats....

It looks like a fail-safe thermostat that fails in the open position to stop overheating.The thermostat should have stampings on the body so look up the part number.If the car had a fail-safe and then failed it likely saved the motor.The picture looks like a new item so another fail-safe is a good idea.

Yep, it's a "test" or flushing thermostst. You were totally correct in removing it. The only valid use is using it during a chemical cooling system flush. You should probably put in the proper 195* thermostat though for good HVAC operation and best engine performance.