This is genuine Fiat part, will fit to thermostat part number:
55206391
You will receive pictured gasket.
For 1.3 Diesel ONLY.
It will fit any Fiat Panda 169 with euro5 engine (2009+) so please check how looks like your current thermostat as for euro4 is different.
It will fit as well 312 version as that's engine continuation of late production 169 euro5.
It will fit 500, 500L, Qubo but please compare photo first.