I'm not an Intellivision gamer by any means but i do happen to have two nice units and recently considered selling them along with maybe two dozen or more boxed games. I noticed one was a 2609 and the other a 2609A. I have yet to find any technical details on the difference between these two units other than an off handed mention they use different screws. I didn't see anything in the FAQ either. So what is the difference?
I also noticed that the controllers fit snugly into the 2609 but not the 2609A plastic. On the 2609 they almost become part of the case, where on the A they extend out the side just a hair. Also, of the four controller (two on each unit) one of them does not have a lip at the top of the controller but is rounded smooth.
And I also noticed that on the 2609 unit the controller cables are excreting an oil but the 2609A's are not. These units have been packed away and stored in climate controlled rooms for decades, so I don't think its an environmental issue.