I have an Atkin (Spring Opener model) serial number 20xx. This was dated by Atkin, Grant and Lang to 1911. It too is No 2 of a pair.
Whilst I agree with Rocketman that the Atkin name doesn't have the desirability of Purdey, Holland or Boss, the Atkin interpretation of the Beesley patent action is regarded as possibly the 'best' interpretation. By that - I mean it is a little smoother and easier to close than others. Mine is certainly wonderfully smooth and 'fluid' to use.