A nice original example of the Improved Moel D, in the rarer .22 calibre. The No.12 peep sight milled into the trigger block makes it aspecially desireable as these are uncommon. They were an expensive extra, which did not sell that well at the time - most people settling for the standard sighting arrangement.
The straighthand stocks are also less common than the pistolhand stocks by about 8 to 1 ( if my collecting experience is anything to go by).
There does seem to be a replacement dome headed screw under the keyhole shaped tap retaining plate, also the locking screw missing, however these could easily be replaced, with spares being obtained from John Knibbs or Chambers.
The gun looks like it could benefit from a rub down with 000 grade wire wool and oil, however apart from that a full service should get it firing a treat. The sporting length (45.5inch) guns packed a punch in the .22 calibre, and were increasingly popular for small game and vermin control, after their launch in mid to late 1908. Your gun can be dated to the end of 1911-early 1912.
Great guns the old BSA's
Lakey