Hi Shawn,

Your best bet is probably the Whois History tool from DomainTools: http://www.domaintools.com/research/whois-history/

This isn't a free service, but they do offer a 7-day free trial.  Also, here are a few more options that might help (they will probably have less information than DomainTools):

http://www.hosterstats.com/ http://www.who.is/

Unfortunately, there's no guarantee that any of these tools will solve your problem (e.g., if the domain has had privacy enabled for many years, you'll just see historically private records), but they're probably your best option.

I hope that helps!

Cheers,
Steve

Short answer: using rel="canonical" to point to the default URL for each product will solve the product-related duplicate content issue.

As for the "best" way to solve this problem, I actually prefer using a robots meta tag with "noindex, follow" attributes on each duplicate product page.

Since the duplicate URLs only exist for navigational purposes, I'd prefer to keep them out of the search engine indexes altogether.

Once you have this issue squared away, be sure to read through these resources for other important eCommerce considerations:

Perfecting On-Page Optimization for Ecommerce Websites

Holy Grail of eCommerce Conversion Optimization