question on M16 selector block

[RCS]

US Military selector block prevents the user from firing full auto on the M16. Can anyone provide any information on the period of use in the service ? I thought it was from the late Viet Nam period but it may even be later. Thanks

[Jersey Devil]

I recently received a pile of these directly from the DoD to install on my agency's M16A2 rifles, so I'm pretty sure they were used considerably later than the Viet Nam era.
My agency-issued M16A2 sports one of these, that I installed, as I type this.....

[RCS]

Thanks for the information

RCS

[Orlando]

Google, M16 selector lock plate NSN 1005-00-233-9031