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This backhead comes with two levers sprued behind and is designed to fit inside the J1 locomotive and later the E1 and Cambrian SPC Class.
As clear photographs and drawings are lacking for these controls on said locomotive classes this has been created using the 21 Class (K2) backhead as a basis and modified in a few areas. Once further information is sourced any potential differencies will be corrected although no guarantee can be given when this may happen.
As the J1 was a rebuild of the E1 Class the controls likely will be the same, if not very similar.
As this backhead is loose and not integrated already into a locomotive body shell; cleaning up, painting and extra detailing with brass tap handles and such like will be much easier. It'll slot in from the top and be a tight fit.