[Premium-Rx] Where is the Digital Pre-selector located in the RF-590

[Gary Mitchelson]

My RF-590 is suppose to have a RF-596A-02 Digital Tuned Bandpass Filter
(per the Harris acceptance tag and a 4 in the Config Code for Pos 3).
The manual says this is an Internal Option and refers to a Supplement. I
have looked inside and see nothing that looks different than what the
manual shows.

Anyone know anything about this option and where it is hiding?