I see a dated discussion on this at http://superuser.com/questions/198710/does-google-chrome-sync-history-between-computers but the important bit there is the Settings.
So it is possible to sync to not sync on some machines according to local settings.
The issue itself is very simple, my browsing history on my main computer for chrome, doesn't always match the history I can see when viewed from a separate machine (a mac). Is there any reasoning why this might happen?

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