For some curious reason, there are 48 observations where the CITY is preceded by the text string ‘ZZ’. There are cases where CITY was misspelled but only one other case I can recall where extraneous characters were inserted before a city name. The PLDF3 schedule of changes for Nebraska documents three cases where the LIBID was also preceded by ‘ZZ’. These cases were only discovered as a result of investigating duplicate entries. It seems unlikely the ZZ’s are random but a quick investigation did not turn up any explanation. Here they are, in order by state:
1992 AZ ZZPhoenix 1992 AZ ZZFlorence 1992 DE ZZGeorgetown 1994 FL ZZClearwater 1995 FL ZZClearwater 1996 IN ZZIndianapolis 1992 LA ZZBaton Rouge 1993 LA ZZBaton Rouge 1994 LA ZZBaton Rouge 1995 LA ZZBaton Rouge 1992 MD ZZCUMBERLAND 1992 MD ZZBALTIMORE 1992 MD ZZSALISBURY 1997 ME ZZPortland 1997 ME ZZSouth Portland 1998 ME ZZSOUTH PORTLAND 1994 MI ZZAnn Arbor 1994 MI ZZAlmont 1994 MI ZZWayne 1995 MN ZZWORTHINGTON 1997 MN ZZROCHESTER 1996 MO ZZJefferson City 1996 NE ZZNiobrara 1997 NE ZZNiobrara 1990 NH ZZCanaan 1993 NH ZZNewport 1994 NH ZZDurham 1992 NJ ZZBound Brook 1993 NJ ZZBound Brook 1989 PA ZZBUTLER 1990 PA ZZCARLISLE 1992 PA ZZBUTLER 1994 PA ZZBELLEFONTE 1995 PA ZZMONESSEN 1996 PA ZZMONESSEN 1996 PA ZZBELLEFONTE 1997 PA ZZBELLEFONTE 1997 RI ZZCoventry 1992 TN ZZHALLS 1992 TN ZZCLARKSVILLE 1992 TN ZZNASHVILLE 1992 TX ZZGalveston 1992 TX ZZAustin 1992 TX ZZKenedy 1992 TX ZZBoerne 1993 TX ZZDallas 1993 TX ZZAmarillo 1996 TX ZZWoodville
Here are the number of these cases by state:
AZ 2 DE 1 FL 2 IN 1 LA 4 MD 3 ME 3 MI 3 MN 2 MO 1 NE 2 NH 3 NJ 2 PA 8 RI 1 TN 3 TX 7
And by year:
1989 1 1990 2 1992 16 1993 5 1994 7 1995 4 1996 6 1997 6 1998 1