Just to update the thread my friend Aaron has replied and apparently the stamp can be found on some of the liners of Mk II's as well he states.
( Not only are they on an lot of the Mk1 liners, they are also found on the Mk2 liners.
Haven't seen the stamp on an post war dated Mk2 liner or lift the dot Mk3 liners.
Don't know the exact name for the stamp, quality control, acceptence stamp or inspectors stamp.
There doesn't seem to be that much info out there about them, what the numbers stand for next to the C^ ? The person who stamps them number, or the maker, again ??? )