I had not spotted that... note that your picture with the larger dome/whistle combo does not have any stickers or tags on the base, making me think it's an earlier/prototype picture. I went to youtube and found a half a dozen or so videos. They all match your picture without the dome, even the wooden box is engraved to match. But, there is a video of the prototype at the Nürnberg toy fair, and that engine does have the large dome. So I guess my thoughts are the large dome was the original idea, but didn't make it to production, unless anyone knows different?