If you look on this page for the SE84UFO you will see down the page a "history of the SE84 amplifier" that gives a breakdown for all the versions, including two forms of the SE84UFOC+
https://www.decware.com/newsite/SE84CKC.htmlHere's the text:
SE84C+
Manufactured from 2008 to 2009.
The chassis was stretched an inch, and the thickness of the steel chassis was doubled. Paint is changed to high-gloss black powder coat. The volume control was moved from the rear to the front. A second set of input jacks was added with a silver switch so you can run two sources.
Current model
SE84C+ for 2010
Manufactured from 2009 to 2012.
Binding posts were upgraded. Finish was changed to a high-gloss piano finish in white. Internally, this amplifier now uses the "CCE" mod that stands for "Christmas Comes Early" and deals with improving the operation of the output-tube suppressor grids.