I've got a Dinky Toys Comet 1 in BOAC colours, G-ALYX, rectangular windows, but, strange to say, blue tail-ie not 100% accurate. I wasn't actually born when the Comet 1 disasters happened, so presumably someone gave me this model (diecast metal) when I was a child in the 1960s.
Must have been something of a rarity even then-and today! If anyone wants to see a photo of this, let me know here, but I won't be able to put it up on my Flickr photostream, with link to it here, till two weeks hence, as I'm going on holiday in a couple of hours.