Hello Jane,
Thank you for replying to my post. Yes, I am still interested in learning more about R.G.C. Soady...5 years ago now one of the persons replying to this post had an RGC Soady in his family tree born in Dublin in the mid 19thC, who became a midshipman on H.M.S. Columbine so that is almost certainly the original owner of the sextant - has to be. If you have some more information about him - or even his sextant- that would be great.
Regards, Stan