The Cerulean Amp Overdrive is an updated version of the Marshall Bluesbreaker pedal. The Bluesbreaker is the source circuit for a number of expensive boutique pedals, including the Analogman King of Tone (which is two Bluesbreakers in the same box with a few modifications).
The Cerulean project has integrated two of the modifications from the King of Tone: the Presence control (an internal trimmer) and the ability to control both the soft clipping (stock) and hard clipping diodes. The clipping switches have been expanded further to allow two different diode combinations for both hard and soft clipping, whereas the King of Tone only has “on” and “off” settings for each.
Another notable clone of the Bluesbreaker is the JHS Morning Glory, which added a JFET gain stage at the end for increased output volume. The Cerulean project provides the option of using the output stage of the Morning Glory.
During the development of this new version of the Cerulean, it was determined that the “Bright Cut” switch of the Morning Glory was not very useful, especially when there was already a Tone control and an internal Presence control, both of which affect the high end. This option has been removed in favor of simplifying the decision-making process when deciding how to build it.
However, if you do want to make an exact clone of the Morning Glory including the Bright switch, you can use the earlier version of the Cerulean which will continue to be available for the foreseeable future.