BAT VK-D5SE DF-PMD100 Upgrade Chip

Is anyone familiar with this upgrade chip for the BAT VK-D5SE cd player? I ran across an ad for it on EBay.but can’t find any info on it. I’ve emailed the seller twice with no response. I’m curious as to what it does and how to install it. The ad states that it replaces an extant chip (the HDCD chip?) and just plugs into its socket but the ad doesn’t show which chip it replaces. It’s supposed to improve the sound of the player but who knows? Just wondering if anyone here knows anything about it?
I have the four tube SE version of this player without the SuperPak.
Thanks,
Sam