The eBay Seller History Tool from Goofbid allows you to view a sellers sale history. You can see exactly what a seller has sold, how many they sold, how much their turnover was and how much they spent in eBay fees.
The eBay Seller History Tool is also extremely useful in learning more about which specific products are working well online. For example, you might know that a retailer does fantastic turnover through their eBay shop, but it might only be a small niche within their product range which is successful for their business.