Can I view past sales

The blue book is great but it does not tell me the condition of the gear sold 
Can I view the original "closed sales" 
You can on Hifi shark. By looking At the open and close dates of closed listings you can tell which sold and you can link through to the original listing. You cannot see the actual selling price however 
The ebay system lets you see past sales, as well as listings that didn't sell. Go to "Advanced search" and put in the component you want to find out about.
Past sales on Audiogon use your imagination.Good luck!!