I've got to come back to the fact that in 1955/56 there was no such thing as an L1/L2 let alone an L8 or an L42 experimental or not.
The development FN rifle was still running thru designations in series from the 1954 X8E1 to an X14E1 until 1957.
Its a range rifle with fantasy markings to excite or defraud the gullible and uninformed.
I've also seen that odd EFD and broad arrow marking before...