I always think that there are 2 questions to answer in cases like this:
1. Are the search engines seeing duplicate content?
2. Could the search engines see duplicate content?
The tools are useful for quickly highlighting potential problems, but you really want to roll your sleeves up and look for yourself. I'll use teh Pneumatic Grippers page as an example:
The title of that page is :"Pneumatic, Grippers, Rotary Actuators, Linear Actuator, Robotics", so I'll do a search for:
intitle:"Pneumatic, Grippers, Rotary Actuators, Linear Actuator, Robotics"
That will bring up everything in google with that page title, just the one result - Good! With regards to that page at least it seems google is only indexing one URL.
The URL that google has indexed is http://www.agi-automation.com/Pneumatic-grippers.htm - as you say, changing that case doesn't affect what page loads, so if an odd case (say http://www.agi-automation.com/PneuMAtic-grippers.htm ) could cause a problem.
What you need to prevent that is a rel=canonical in the source (I checked, you don't). That tells the search engine what the correct address is. Just ensure you have something like the following in your head section
http://www.agi-automation.com/Pneumatic-grippers.htm" />
There is another way to do it, redirecting the "wrong" version of URLs, but rel=canonical looks like the right choice for your site.
What I would say though, is this: If the search engines aren't picking up duplicate copies don't panic too much over this. It would be good to have it, but it is only a big issue if duplicate pages are actually being indexed. If not it is good insurance.
I hope that helps