new marantz sc7 and sm7 system I bought from Japan in 1979.

Constructed with an untold number of electrolytic capacitors, that are now over 37 years old, it would be a good idea to be certain the pieces are actually functional, before trying to sell them. What you get will depend on the yen a buyer might have for old SS Marantz gear.

To add to what Rodman said, what voltage are they?  If not US, they will need a step/up transformer.

I bought these from Tokyo's Akihabara Electric Town.  These were built for US market and are have adjustable voltages for multiple countries (110v to 240 volts).  They have the US electrical cords.  I have used them with US and European voltages. These are the Gold Anodized versions.  They are awesome when the system is setup.  I bought a set of the big Pioneer speakers from Japan also along with the Top of the line Pioneer PL1000 turntable that has also been boxed since 1982.  I have many other vintage stereo electronics that I purchased from Japan that are also in mint condition.  Dynamic Range expanders, equalizers, Teac tape decks, akia reel-to-reel tape decks, All are with original papers, manuals, and boxes.

You,  "...have used them with US and European voltages." and they're still, "brand new"?   Neat trick!