A PO BOX number can be less than or more than four digit. For post office boxes, the general rule is that each box has its own ZIP+4 code.
The last four digit is often one of the following:
1. Zero plus the last three digits of the box number (eg. PO BOX 1001, Los Angeles CA 90001-0001).
2. The last four digits of the box number (eg. PO BOX 9991, Twin Peaks CA 92391-9991).
3. If the box number is less than four digits, enough zeros prepended to the front of the box number to produce a four-digit number(eg. PO BOX 1, Shreveport LA 71161-0001).
However, there is no uniform rule, the zip code plus four is for reference only, the ZIP+4 code must be looked up individually for each box in the USPS offical website.
PO BOX 21, DUNCAN, OK 73534-0021
PO BOX 22, DUNCAN, OK 73534-0022
PO BOX 23, DUNCAN, OK 73534-0023
PO BOX 24, DUNCAN, OK 73534-0024
PO BOX 25, DUNCAN, OK 73534-0025
PO BOX 26, DUNCAN, OK 73534-0026
PO BOX 27, DUNCAN, OK 73534-0027
PO BOX 28, DUNCAN, OK 73534-0028
PO BOX 29, DUNCAN, OK 73534-0029
PO BOX 30, DUNCAN, OK 73534-0030
PO BOX 31, DUNCAN, OK 73534-0031
PO BOX 32, DUNCAN, OK 73534-0032
PO BOX 33, DUNCAN, OK 73534-0033
PO BOX 34, DUNCAN, OK 73534-0034
PO BOX 35, DUNCAN, OK 73534-0035
PO BOX 36, DUNCAN, OK 73534-0036
PO BOX 37, DUNCAN, OK 73534-0037
PO BOX 38, DUNCAN, OK 73534-0038
PO BOX 39, DUNCAN, OK 73534-0039
PO BOX 40, DUNCAN, OK 73534-0040
PO BOX 41, DUNCAN, OK 73534-0041
PO BOX 42, DUNCAN, OK 73534-0042
PO BOX 43, DUNCAN, OK 73534-0043
PO BOX 44, DUNCAN, OK 73534-0044
PO BOX 45, DUNCAN, OK 73534-0045
PO BOX 46, DUNCAN, OK 73534-0046
PO BOX 47, DUNCAN, OK 73534-0047
PO BOX 48, DUNCAN, OK 73534-0048
PO BOX 49, DUNCAN, OK 73534-0049
PO BOX 50, DUNCAN, OK 73534-0050
PO BOX 51, DUNCAN, OK 73534-0051
PO BOX 52, DUNCAN, OK 73534-0052
PO BOX 53, DUNCAN, OK 73534-0053
PO BOX 54, DUNCAN, OK 73534-0054
PO BOX 55, DUNCAN, OK 73534-0055
PO BOX 56, DUNCAN, OK 73534-0056
PO BOX 57, DUNCAN, OK 73534-0057
PO BOX 58, DUNCAN, OK 73534-0058
PO BOX 59, DUNCAN, OK 73534-0059
PO BOX 60, DUNCAN, OK 73534-0060
PO BOX 61, DUNCAN, OK 73534-0061
PO BOX 62, DUNCAN, OK 73534-0062
PO BOX 63, DUNCAN, OK 73534-0063
PO BOX 64, DUNCAN, OK 73534-0064
PO BOX 65, DUNCAN, OK 73534-0065
PO BOX 66, DUNCAN, OK 73534-0066
PO BOX 67, DUNCAN, OK 73534-0067
PO BOX 68, DUNCAN, OK 73534-0068
PO BOX 69, DUNCAN, OK 73534-0069
PO BOX 70, DUNCAN, OK 73534-0070
PO BOX 71, DUNCAN, OK 73534-0071
PO BOX 72, DUNCAN, OK 73534-0072
PO BOX 73, DUNCAN, OK 73534-0073
PO BOX 74, DUNCAN, OK 73534-0074
PO BOX 75, DUNCAN, OK 73534-0075
PO BOX 76, DUNCAN, OK 73534-0076
PO BOX 77, DUNCAN, OK 73534-0077
PO BOX 78, DUNCAN, OK 73534-0078
PO BOX 79, DUNCAN, OK 73534-0079
PO BOX 80, DUNCAN, OK 73534-0080
PO BOX 81, DUNCAN, OK 73534-0081
PO BOX 82, DUNCAN, OK 73534-0082
PO BOX 83, DUNCAN, OK 73534-0083
PO BOX 84, DUNCAN, OK 73534-0084
PO BOX 85, DUNCAN, OK 73534-0085
PO BOX 86, DUNCAN, OK 73534-0086
PO BOX 87, DUNCAN, OK 73534-0087
PO BOX 88, DUNCAN, OK 73534-0088
PO BOX 89, DUNCAN, OK 73534-0089
PO BOX 90, DUNCAN, OK 73534-0090
PO BOX 91, DUNCAN, OK 73534-0091
PO BOX 92, DUNCAN, OK 73534-0092
PO BOX 93, DUNCAN, OK 73534-0093
PO BOX 94, DUNCAN, OK 73534-0094
PO BOX 95, DUNCAN, OK 73534-0095
PO BOX 96, DUNCAN, OK 73534-0096
PO BOX 97, DUNCAN, OK 73534-0097
PO BOX 98, DUNCAN, OK 73534-0098
PO BOX 99, DUNCAN, OK 73534-0099
PO BOX 100, DUNCAN, OK 73534-0100
PO BOX 101, DUNCAN, OK 73534-0101
PO BOX 102, DUNCAN, OK 73534-0102
PO BOX 103, DUNCAN, OK 73534-0103
PO BOX 104, DUNCAN, OK 73534-0104
PO BOX 105, DUNCAN, OK 73534-0105
PO BOX 106, DUNCAN, OK 73534-0106
PO BOX 107, DUNCAN, OK 73534-0107
PO BOX 108, DUNCAN, OK 73534-0108
PO BOX 109, DUNCAN, OK 73534-0109
PO BOX 110, DUNCAN, OK 73534-0110
PO BOX 111, DUNCAN, OK 73534-0111
PO BOX 112, DUNCAN, OK 73534-0112
PO BOX 113, DUNCAN, OK 73534-0113
PO BOX 114, DUNCAN, OK 73534-0114
PO BOX 115, DUNCAN, OK 73534-0115
PO BOX 116, DUNCAN, OK 73534-0116
PO BOX 117, DUNCAN, OK 73534-0117
PO BOX 118, DUNCAN, OK 73534-0118
PO BOX 119, DUNCAN, OK 73534-0119
PO BOX 120, DUNCAN, OK 73534-0120
PO BOX 121, DUNCAN, OK 73534-0121
PO BOX 122, DUNCAN, OK 73534-0122
PO BOX 123, DUNCAN, OK 73534-0123
PO BOX 124, DUNCAN, OK 73534-0124
PO BOX 125, DUNCAN, OK 73534-0125
PO BOX 126, DUNCAN, OK 73534-0126
PO BOX 127, DUNCAN, OK 73534-0127
PO BOX 128, DUNCAN, OK 73534-0128
PO BOX 129, DUNCAN, OK 73534-0129
PO BOX 130, DUNCAN, OK 73534-0130
PO BOX 131, DUNCAN, OK 73534-0131
PO BOX 132, DUNCAN, OK 73534-0132
PO BOX 133, DUNCAN, OK 73534-0133
PO BOX 134, DUNCAN, OK 73534-0134
PO BOX 135, DUNCAN, OK 73534-0135
PO BOX 136, DUNCAN, OK 73534-0136
PO BOX 137, DUNCAN, OK 73534-0137
PO BOX 138, DUNCAN, OK 73534-0138
PO BOX 139, DUNCAN, OK 73534-0139
PO BOX 140, DUNCAN, OK 73534-0140
PO BOX 141, DUNCAN, OK 73534-0141
PO BOX 142, DUNCAN, OK 73534-0142
PO BOX 143, DUNCAN, OK 73534-0143
PO BOX 144, DUNCAN, OK 73534-0144
PO BOX 145, DUNCAN, OK 73534-0145
PO BOX 146, DUNCAN, OK 73534-0146
PO BOX 147, DUNCAN, OK 73534-0147
PO BOX 148, DUNCAN, OK 73534-0148
PO BOX 149, DUNCAN, OK 73534-0149
PO BOX 150, DUNCAN, OK 73534-0150
PO BOX 151, DUNCAN, OK 73534-0151
PO BOX 152, DUNCAN, OK 73534-0152
PO BOX 153, DUNCAN, OK 73534-0153
PO BOX 154, DUNCAN, OK 73534-0154
PO BOX 155, DUNCAN, OK 73534-0155
PO BOX 156, DUNCAN, OK 73534-0156
PO BOX 157, DUNCAN, OK 73534-0157
PO BOX 158, DUNCAN, OK 73534-0158
PO BOX 159, DUNCAN, OK 73534-0159
PO BOX 160, DUNCAN, OK 73534-0160
PO BOX 161, DUNCAN, OK 73534-0161
PO BOX 162, DUNCAN, OK 73534-0162
PO BOX 163, DUNCAN, OK 73534-0163
PO BOX 164, DUNCAN, OK 73534-0164
PO BOX 165, DUNCAN, OK 73534-0165
PO BOX 166, DUNCAN, OK 73534-0166
PO BOX 167, DUNCAN, OK 73534-0167
PO BOX 168, DUNCAN, OK 73534-0168
PO BOX 169, DUNCAN, OK 73534-0169
PO BOX 170, DUNCAN, OK 73534-0170
PO BOX 171, DUNCAN, OK 73534-0171
PO BOX 172, DUNCAN, OK 73534-0172
PO BOX 173, DUNCAN, OK 73534-0173
PO BOX 174, DUNCAN, OK 73534-0174
PO BOX 175, DUNCAN, OK 73534-0175
PO BOX 176, DUNCAN, OK 73534-0176
PO BOX 177, DUNCAN, OK 73534-0177
PO BOX 178, DUNCAN, OK 73534-0178
PO BOX 179, DUNCAN, OK 73534-0179
PO BOX 180, DUNCAN, OK 73534-0180
PO BOX 181, DUNCAN, OK 73534-0181
PO BOX 182, DUNCAN, OK 73534-0182
PO BOX 183, DUNCAN, OK 73534-0183
PO BOX 184, DUNCAN, OK 73534-0184
PO BOX 185, DUNCAN, OK 73534-0185
PO BOX 186, DUNCAN, OK 73534-0186
PO BOX 187, DUNCAN, OK 73534-0187
PO BOX 188, DUNCAN, OK 73534-0188
PO BOX 189, DUNCAN, OK 73534-0189
PO BOX 190, DUNCAN, OK 73534-0190
PO BOX 191, DUNCAN, OK 73534-0191
PO BOX 192, DUNCAN, OK 73534-0192
PO BOX 193, DUNCAN, OK 73534-0193
PO BOX 194, DUNCAN, OK 73534-0194
PO BOX 195, DUNCAN, OK 73534-0195
PO BOX 196, DUNCAN, OK 73534-0196
PO BOX 197, DUNCAN, OK 73534-0197
PO BOX 198, DUNCAN, OK 73534-0198
PO BOX 199, DUNCAN, OK 73534-0199
PO BOX 200, DUNCAN, OK 73534-0200
PO BOX 201, DUNCAN, OK 73534-0201
PO BOX 202, DUNCAN, OK 73534-0202
PO BOX 203, DUNCAN, OK 73534-0203
PO BOX 204, DUNCAN, OK 73534-0204
PO BOX 205, DUNCAN, OK 73534-0205
PO BOX 206, DUNCAN, OK 73534-0206
PO BOX 207, DUNCAN, OK 73534-0207
PO BOX 208, DUNCAN, OK 73534-0208
PO BOX 209, DUNCAN, OK 73534-0209
PO BOX 210, DUNCAN, OK 73534-0210
PO BOX 211, DUNCAN, OK 73534-0211
PO BOX 212, DUNCAN, OK 73534-0212
PO BOX 213, DUNCAN, OK 73534-0213
PO BOX 214, DUNCAN, OK 73534-0214
PO BOX 215, DUNCAN, OK 73534-0215
PO BOX 216, DUNCAN, OK 73534-0216
PO BOX 217, DUNCAN, OK 73534-0217
PO BOX 218, DUNCAN, OK 73534-0218
PO BOX 219, DUNCAN, OK 73534-0219
PO BOX 220, DUNCAN, OK 73534-0220
PO BOX 221, DUNCAN, OK 73534-0221