Good advice, but still this stat that's blocked off / not drilled, what possible application would there be for any use.
It would have to be for an engine that doesn't have a heating system, but yet still has heater matrix pipework.
The coolant flows into the matrix via the long plastic pipe at the bottom of the stat, circulates through the matrix, then comes to the dead end, but can flow down back to the feed pipe.
Although it can't contine around the matrix again due to flow speed. Instead there's a pressure build up in the stat housing which then pushes the front of the stat off.
On my car, after "rigorous" testing and wondering how I was getting coolant sprayed onto the fan shroud.
With the engine warm but the start closed and with high revs applied you could watch it lift out and fire the coolant out.