A copper colored 1861?

So these are from an ebay auction that is current - It's just weird - the movement looks like a standard 861, but as the seller points out, where it should have the omega symbol and "861" it has an "1861". The serial number is in the 32xxxxxx range, so I can't see how this would be marked 1861 unless it was a genuine mistake when the movement was being made. I won't link the auction as I don't want to violate any rules, but it is listed as "Omega Speedmaster Professional Moon Watch.ST145.022 w/Step Dial READ DESCRIPTION"

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