Bob, it appears to be a straight, non-taper sinking line, which is not bad. In fact, I was in Chile, early February, using a 5wt for trout with a level sinking line. It cast fine with a streamer.
As a sidebar, we use a lot of sinking shooting heads on the Cape that are level lines, eg LCD-13, T-14 etc. they work well. See you this Spring.