Oddly enough, just today I have moved the top front lamp iron and the whistle on my own O4, and this has revealed something I didn't notice. On the cab roof Bachmann have reproduced a bolted-on patch, presumably added to the real locos to cover the hole where the whistle first was. It seemed to me a reasonable idea to drill through the middle of the patch and insert a whistle (picture to follow later). Only with hole drilled and whistle inserted, could I THEN see that the patch isn't quite central
on the roof
I've consulted drawings, but none of my reliable ones include a view that shows whether the whistle was central. Ground level photos are of little help, but I did find a shot in John Hooper's "LNER sheds in Camera" book, taken in 1935 at Doncaster, from a very high viewpoint. In that, there's an ROD with its whistle already placed in front of the cab, and a GC built O4 whose cab-roof whistle probably
appears to be central. If that observation is right then my whistle is wrong.
Does anybody know the truth?
Image added as promised:
Even here it is hard to see that the patch and whistle are slightly offset to the right (driver's) side of the loco, i.e. away from the viewer, but they are!