The Gold and Veteran (crimson) Berets were given to players who purchased the 1.0 Gold Upgrade prior to Unturned's launch into Steam Early Access on the 7th of July 2014. Back then the Gold Upgrade was associated with an account on the SDG website. They were a special thank you to the supporters who helped bring Unturned to Steam.
If you remember your account details from the SDG website but didn't redeem these items back then please submit a request. Again to clarify: please only submit the request if you played before the launch into Early Access. (2014-07-07)