http://pe.usps.com/archive/html/dmmarch ... m#Raq2180010.0 Motor Vehicle Master Keys and Locksmithing Devices
10.1Motor Vehicle Master Key—Definition
A motor vehicle master key is any key (other than the key furnished by the manufacturer with the motor vehicle, or the key furnished with a replacement lock, or an exact duplicate of such keys) designed to operate two or more motor vehicle ignition, door, or trunk locks of different combinations, including any pattern, impression, or mold from which such a master key can be made (18 USC 1716A; 39 USC 3002).
10.2Nonmailable
Any motor vehicle master key, as defined in 10.1, and any advertisement for the sale of such item, are nonmailable, unless sent to any of the following:
a. Lock manufacturer.
b. Professional locksmith.
c. Motor vehicle manufacturer or dealer.
d. Federal, state, or local government agency.
10.3Marking
Any marking identifying the contents is not permitted on the outside wrapper or container of any parcel containing motor vehicle master keys.
10.4Locksmithing Device—Definition
A locksmithing device is:
a. A device or tool (other than a key) designed to manipulate the tumblers in a lock into the unlocked position through the keyway of such lock.
b. A device or tool (other than a key or a device or tool under 10.4a) designed for bypassing a lock or similar security device, or for opening it by a method normally not used by consumers to open such locks or security devices.
c. A device or tool designed for making an impression of a key or similar security device to duplicate such key or device.
10.5Nonmailable
Any locksmithing device, as defined in 10.4, is nonmailable, unless sent to any of the following:
a. Lock manufacturer or distributor.
b. Bona fide locksmith.
c. Bona fide repossessor.
d. Motor vehicle manufacturer or dealer.
e. Bona fide automotive repair shops or businesses.
Take a look at section 10.4 10.5
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