New and reviewed in the December 1956 issue of Popular Mechanics, the Mercury Scientific Products Corp. manufactured DIS-CHARGER is somewhat of a mystery in 2015. We know it helps to keep records dust and static free, but we don’t know how! (Quick Google search) Ah-ha! We do now! From the mouths of babes (or mechanic nerds from 1956), here is, verbatim, how the Mercury Scientific Products Corp. DIS-CHARGER flawlessly functions:
Records will sound better and last longer when tiny Dis-Charger, Fig. A, is clipped to record-player tone arm. Unit draws off static charge as record is played, releasing injurious and noise-producing dust clinging to record grooves. – Popular Mechanics, December, 1956 (page 157)
(photo courtesy of Popular Mechanics, and is used entirely without permission)
The Prudent Groove 
It gets better! Turns out there was radioactive material in these static dischargers! Here’s the relevant article in Billboard: https://books.google.com/books?id=fx4EAAAAMBAJ&lpg=PA23&ots=cJIg_U2t_g&dq=dis-charger%20mercury%20scientific%20products&pg=PA23#v=onepage&q=dis-charger%20mercury%20scientific%20products&f=false
That’s insane! Thanks for the info! (Sorry for the late reply!)
I have one still in the box. Complete with instructions. I checked it with a Geiger counter and it is, in, fact slightly radio active.
Ha!! That’s crazy!