[Andy01 (Andy)]

Perfect condition - loaded into my filterwheel once, and only selling because I recently invested in 3nm version.

When it comes to Narrowband filters, no one knows more or does it better than Don Goldman of Astrodon Filters. Narrowband (NB) filters enhance contrast of emission objects by accepting only a narrow range of wavelengths around the emission lines of hydrogen (H-a, 656 nm), oxygen (OIII, 501 nm), sulfur (SII, 672nm) and others.

Astrodon filters can be used to image when the moon is up, thereby extending imaging time and can be used in light-polluted locations.
This 5nm FWHM H-a filter for 656.3 nm also includes NII emission at 658.4 nm.

I've used this filter with great sucess, picking up the David Malin Deep space category award in 2015.

This will cost in excess of $520 to land in Australia.
I'll let you have it for $350 inspection welcome, posted anywhere in Australia.
Photo of actual filter below.