1885:
The small JA in a circle is the initial or Trade Mark for Josh Astbury, an action forger and filer, and parts machinist, for the trade. He operated from a workshop in the Birmingham gun quarter between the wars (and maybe earlier guessing the age of your Andrews hammergun). I have also seen his name written as Joseph Astbury (perhaps the next/previous generation?), and also the spelling 'Asbury'. Unfortunately, not much is known about the firm since they never made-up complete guns. Nevertheless, some very high quality guns wear this mark, including my Manton-retailed John Wilkes .470!

Although plain-finished, you can be very confident that your double is indeed a good one, 1885.