Quite possibly the initials of the Officer who found the exhibit, followed by the number of exhibits he/she found. That is my Court experience, corroborated by a quick call to my local Police Department (the poor guys are open on Sundays so they can be imposed upon by nosey translators)
With that said, and given no further text before and after, my C.L. is medium.
The other options I found on line give: Psychiatric Social Worker and Program Status Word (by far the one with most hits), but they seem inconsitent with your subject.