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It could, but it's mostly a broken way to go about doing it. Per Google's guide on it: https://support.google.com/webmasters/answer/181708, "Because of the time Googlebot spends on non-existent pages, your unique URLs may not be discovered as quickly or visited as frequently and your site’s crawl coverage may be impacted (also, you probably don’t want your site to rank well for the search query [File not found])."  So it's best to fix them to either return a custom 404 page, redirect via 301, or correctly land on a page of content without the 404.

Hi There! Sorry that wasn't what you needed. Basically, no, so far as I know, there is no obvious visual signal looking through Bing Places that a listing has been verified. If you click on the 'report a problem' link at the bottom of a Bing Place page, it takes you to a page that says 'Are you the business owner, claim this listing', but unfortunately, it appears to do this whether the listing is claimed or not. So, that's kind of weird. As an experiment, you could attempt to go through the claiming process of a listing you are curious about and see if it eventually stops you with a 'this is already claimed' message. This is the only test I can think of to run. Hope it's at least somewhat helpful to know you're not missing some obvious visual signal. There just doesn't appear to be one, nor can I find any documentation that such a signal exists.

It looks like your current set up is smart- the domain authority wont change regardless of www since that is a subdomain. Also, the rel canonical redirection strategy  would not be as effective as a 301 redirect in most cases.