This is a nice no. 0 size (7/8" threading but for a smaller lamp) antique brass oil or kerosene lamp hardware, a P&A "Hornet" with a working wick and paired with the appropriately-sized clear glass chimney.

Approximate meausurements (may vary slightly):

     Brass hardware with 7/8" collar threading

     Chimney is is about 4 3/4" high with a 1 1/2" fitter rim

Nice antique condition exactly as shown; hardware is in nice conditih with wick installed and thumbwheel working to advance exactly as designed, chimney has a little roughness and flaking to rims - nothing major.