Actually the newer one isn't fully closed. There is a diamond shaped, molded hole in the filler piece that is necessary to prevent a vacuum from forming (water wouldn't flow). I originally thought this hole was damage to the first one I examined until I realized they all have this. Preventing a vacuum is why (I presume) that the rear of the older sprayer was fully open as well. BUT, for as little as things seemingly changed on belt-drive machines, small changes like this were made all over the machines throughout their production lives. I'm guessing that WP thought they were better or more cost effective, etc.
Gordon
