This would vary depending on where the RE are being shipped from and how long have those been on the shelves.
Since most MX are built to order, i would think if you order the latest 64 bit RE you'll get a new-ish code on those. and if you order the older REs, you'll get and older code.
Always plan to upgrade/downgrade to the code you seem most appropiate.
I hope that helps.
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