Not wanting to break the plastic petcock I need to ask...what type of
design is it? Is it a traditional CCW screw-all-the-way-out type or just a
1/4-turn type valve?

I was getting ready to drain the coolant system and when I proceeded to turn
the petcock it turned very easily in a CCW direction for about 1/4 turn then
stopped solid. It still easily turns back and forth that 1/4 turn ans
exhibits loosness in the threads but no coolant drains (pressure cap
removed). I'm expecting it's designed to unscrew a few turns to release
coolant but would like to make sure prior to creating a real problem.

Cheers,
Tj