Looks to be MOS-U, which I have as 1955. From what I've seen, JC Higgins didn't offer a full, flashy deluxe model in 1955. It could have been due, in part, to the strikes at the Murray factory which caused much of the manufacturing year to be outsourced to Austria.
1954 was the last year the Colorflow was offered, and 1956 introduced the Jetflow. So I think this may have been the most deluxe available for '55. They possibly offered it with a light and springer, though. Can anybody confirm this? I can't locate a 1955 Sears catalog to check.