as i recall we had 2 letters first. #1 was location (we had one big histo lab processing for ~15 locations), #2 was type of specimen( inpatient,outpatient,derm,) followed by the accession sequence followed by the year.
BI-4444-98 is from Bad hospital, inpatient, 4,444th case of 1998.
If this isn’t exactly right folks, remember i’m the “old guy” on the board retired 9 yrs[emoji6]