LNER GRESLEY A3 CLASS LOCOMOTIVE KIT
A BRIEF HISTORY.
Just before Grouping, Nigel Gresley introduced his prototype 4-6-2 design on the GNR. There were only two engines of this class in service at the end of 1922, but a further ten had been ordered by the GNR and these were completed in 1923, the LNER classification being A1.  On Gresley's appointment as CME of the LNER this class was adopted as standard and a further forty (twenty by the North British Locomotive Company) were constructed in 1924-25.  In 1927 two of the class were rebuilt with higher pressure boilers to become the first of class A3 and eventually, by 1948, all but the first engine were dealt with in this fashion.  These engines were all built with the driving position on the right hand side.  Between 1927 and 1931 the original valve gear with short valve travel (STV) was replaced with a new design with increased travel long travel valves (LTV).   
During 1928-35, twenty-seven new A3's were built with the driving position on the left hand side.  These engines had the long travel valves and were built under 3 Engine Orders.

During 1952-54 the remaining fifty-one of the original engines were eventually converted to left hand drive. 
So from this kit, which is for left hand drive engines, the twenty-seven new A3's can be built in their original condition and the remaining engines can be built after their conversion to left hand drive.  

For a detailed history of this long lived class Part 2A of Locomotives of the LNER published by the RCTS is essential reading. Other valuable sources of information and photographs are: 
The Book of the A3 Pacifics by Peter Coster. 
The Power of the A3s by Gavin Morrison.
Locomotives Illustrated 25 - Ian Allan   
The Gresley Pacifics - O.S.Nock - David & Charles 
Yeadon's Register of LNER Locomotives - Volume One - Irwell Press 
East Coast Pacifics at Work - P.N.Townend - Ian Allan 
The Power of the A1s, A2s and A3s - J.S.Whiteley & G.W.Morrison - Oxford Publishing Co
Isinglass Drawings 329-333

VARIATIONS POSSIBLE WITH THE KIT.
Chimney.
   Original type and double chimney fitted to most of the locomotives from 1958 onwards. 

Dome.   Original type and later banjo dome. 

Frames.  There were differing frame lightening hole arrangements. All locomotives had the hole ahead of the cylinders. In addition EO's 314 & 317 had four circular holes, 12" in diameter. Locomotives from EO 331 only had the hole ahead of the cylinders. The locomotives originally built as A1 had the four larger oval holes.
 
Frame rivets.  The original engines were built using countersunk rivets and so give a smooth appearance to the frames. Many photographs show a gradual change to rivets with a visible head as frames were repaired or replaced. 

Bogie.  The locomotives built with the swing link bogies were soon converted to the helical spring type circa 1933-34.

Front end cover plates. Small cover fitted from 1933 onwards and larger sliding cover from 1945. 

Front footsteps.  Fitted from 1935 onwards. 

Rear spring retaining brackets.  Fitted later.
 
Firebox crown washout plugs/door covers.  Originally square ended plugs and from circa 1936 onwards circular covers. 

Anti-vacuum valve plate.  Two types provided. 

Cab seats.  Original type replaced with bucket seats from circa 1935 onwards. 

Cab sides. Original cut-out increased in height by 11" at the same time as bucket seats fitted. 

Lamp irons - footplate.  Second lamp iron on RHS removed from 1931. 

Lamp iron - smoke box door.  Two different types.
 
Trough type smoke deflectors.  Fitted to 55 of the locomotives from 1960 onwards. 

Reversing rod.  Different shape depending on whether Doncaster or North British built.
 
Frame guard irons.  Removed in the period 1952-54.