The silencer must be marked in accordance with 27 C.F.R. §§ 478.92 and 479.102. The regulations require that the markings be conspicuous and legible, meaning that the markings may be placed on any external part, such as the outer tube or end cap.
ATF strongly recommends that manufacturers place all required markings on the outer tube of the silencer, as this is the accepted industry standard. Moreover, this practice eliminates the need to remark in the event an end cap bearing the markings is damaged and requires replacement.