This is an  excellent example of the Wrenn W2215 N2 Tank Locomotive in LMS Black, running number 2385. Introduced by Wrenn, Basildon in  Period 2 (Triang/Wrenn), this continued in production through Period 3 and into Period 4.   

This particular example is from early Period 3 (circa 1972) build, and is becoming difficult to find today in this condition. As with all Period 3 locomotives it has "metal rimmed" bogie wheels correct for P3 Basildon issue. 

Comes complete in P3 box, including tissue, packing rings, Hornby Dublo coupling conversion kit and single page Instruction Sheet. 

The bottom of the inner box has the familiar sellotape residue marks  indicating Period 3 Basildon issue. 

Condition of Locomotive/box is "near mint " considering age.