12.7 x 110 French Experimental

Below is a picture of the ‘standard’ 12.7x110 experimental case. Beside (on the right) it is what appears to a 14 x 110. The case neck measures 15.2 mm on the outside and ca 14.1 mm inside. Today I learned that there is another variation which is headstamped “20mm” at 12 o’clock and “LUM-1-70” at 6 o’clock indicating that whatever test this case was used in did not occur before 1979. Does anyone have any information on this 14 x 110?