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Our website shows ~22k pages in the sitemap but ~56k are showing indexed on Google through the "site:" command. Firstly, how much attention should we paying to the discrepancy? If we should be worried what's the best way to find the cause of the difference?

The domain canonical is set so can't really figure out if we've got a problem or not?

Are there any implications of using two page description properties, i.e.

meta name="<a class="attribute-value">description</a>" and meta property="<a class="attribute-value">og:description</a>"

We've recently been approached by a new client who's had a 60%+ drop in organic traffic. One of the major issues we found was around 60k+ pages of content duplicated across 3 seperate domains. After much discussion and negotiation with them; we 301'd all the pages across to the best domain but traffic is increasing very slowly.

Given that the old sites are 60k+ pages each and don't get crawled very often, is it best to notify the domain change through Google Webmaster Tools to try and give Google a 'nudge' to deindex the old pages and hopefully recover from the traffic loss as quickly and as much as possible?