Hi all,
this adapter is the Starlight Instruments A35-505AP-1, and is surplus to my needs. It threads into any 2.7" Astro Physics threaded end caps to Convert 'AP Threaded End Cap' to 'SBIG STL 11000' Threads
This part is designed to thread directly into an Astro Physics threaded end cap.
Details here
http://starlightinstruments.com/stor...product_id=230
New price is USD $75+$55 postage (!!), so about AUD$170.
It's in perfect condition, sell for AUD$110 posted