It's never been that way in Marion County. Ever.
Edit to clarify:
IPD/IMPD use the a,b,d, etc plus three numbers to signify their "unit number" unless it's a k9 officer, and then it is k_ _. The Letter involved is not based on their last name. Marion County Sheriff's Office uses S_ _ _. (all of these numbers, of course, can be shortened with higher rank.
My mistake. The years have not been good to me. My radio (unit number) was 957. My ID (can not remember what it's called) was P + last 4 of my SSN. That is the number the OP should ask for.