I've had counterfeit parts for Hueys and Jetbangers (millions of 'em made in Vietnam after their war) mainly made from Brass instead of Ally! All painted up well and good castings - non-magnetic, but too heavy.
Also found one 206BII Rotor Head with no Serial Number (optional extra?) All reported to civil authorities very quickly.
However, I've also seen many genuine parts installed well past their official lives have expired due to lack of control in military regimes. All "forgotten" very quickly...