Up for sale here is a set of 1.25" Antlia 3.5nm SHO filters purchased in September last year. Only selling because I'm getting out of imaging. Very good condition, lived their whole life in a filter wheel.
New price was about $890 posted from the US at current exchange rates. Asking $600 posted within Australia.
Here's a couple of images taken with these filters:
https://www.astrobin.com/full/bre26x/B/
https://www.astrobin.com/full/nvy2hd/0/