Very thorough Duck, honestly did even know what those numbers on the bottom meant at first.
But I do believe that these could've had the potential to be different releases still.
Proteus did have a New Friends release and a Little Friends release too, but I think these must both be New Friends releases if they're only 5 days apart.
And I believe the packaging of the New Friends releases could prove that.
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So here's what his New Friends Packaging looks like:
Here's what I believe is his very first variant, and essentially the Proteus model that could've been his first one with "Made in China" stamped on it.
I do own one myself, and this is what the second version of the box looks like:
The one difference is that his "New Friend!" Label is gone, which I think is a sign of which came first.
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So I think that the factory codes and dates definitely trace back only to his New Friends releases.
The "Made in China" one could be the Proteus with the "New Friend!" Label, and the one missing the label doesn't have "Made in China" stamped on it.
Based also on the information from the Thomas Motorized Wiki, The TOMY version first came out in November, and the Little Friends version only came out throughout 2009. So these Proteus models can't be either of those two. Leading me to think you've got two New Friends Proteusi (I like Proteusi quite a lot more than Proteuses) Hoser, only from two different types of packaging back in October. I think the switch of the packaging was possibly done at a different day, like October 5th or 6th maybe. And then they just re-printed the model from scratch. Why they would discontinue a version with the "New Friend!" Label is unknown to me, but I think this is what happened. If I had a used Proteus I could look at it much closer, but I've only got a BNiB one. So I can only use what I've got, and what I've got is one possibly without the "Made in China" print.