It’s a good theory but I don’t think it’s quite right. All full size Blake 3 hand and GMT models are the same ~41mm, it’s just they changed how they quoted the size on the website at some point. Also the last Blake dial 1120 movement models were made in 2006 so a little earlier than you suggest maybe. I do agree on the bracelet differences you state. The white border is never seen on some models like the 2531 or 2254, but on others it’s seen on some examples and not others. Not sure which is earlier, with or without. Note a quick search throws up 2231 and 2232s with or without the border but it could be a case of misidentification by sellers I guess.
