If any person receives any mail bag, or any postal packet or any chattel or money or valuable security, the stealing . . . F2 or secreting of which amounts to F3an offence under this Act, knowing it to have been so . . . F4 stolen . . . F2 or secreted, and to have been sent, or to have been intended to be sent, by post, he shall F5be guilty of a misdemeanour and be liable to imprisonment for a term not exceeding fourteen years and may be proceeded against and convicted whether the principal offender has or has not been previously convicted or is or is not amenable to justice.