46 48 50 52 and protrusions 54 56 58 60 62 64 the protrusions vary in width as shown by large protrusions 54 56 and small protrusions 58 60 62 64 the indentations also vary in width as shown by small indentations 42 44 48 as opposed to large indentations 46 50 52 the marking elements can also be distinguished by their locations on the lands 34 36 and grooves 38 40 lands 34 36 have a large protrusion 54 small protrusions 62 64 large indentation 50 and small identations 42 44 grooves 38 40 have large protrusion 56 small protrusions 58 60 large indentations 46 52 and small identation 48 an array 66 of marking elements similar to the array of fig7 is shown in the context of a whole barrel bore 68 in fig6 using this variety of possible arrays a code can be established in which marking elements are organized in such a manner that individual numerals and letters are assigned to certain combinations of marking elements most firearms have identification numbers which are usually a series of numerals or a combination of numerals and letters using the predetermined code the identification number of a firearm is represented on the bore surface of the firearm in the form of an array of marking elements any bullet fired from that firearm will be marked with markings corresponding to that firearm 39 s array of marking elements using the code the identity of the firearm from which a bullet came can be determined by reading the bullet surface the particular code used is not a part of.