I have had this unit several years and was wondering where I could buy blank recording discs since it has a recording tone arm in addition to the regular tone arm. Since I don't see a linear drive mechanism I assume the record must have a blank spiral cut initially and then the recording tone arm would follow it cutting the groove with the sound.
If this is mistaken I would appreciate clarification on the subject.

You can get discs here.

http://www.apollomasters.com/index.html

I'm pretty sure that is a home recording unit. I don't have any experience with the Sparton, but most all of your home units don't have the automatic feature of start and ending grooves. Most are cutting arms ride on a feed screw and you just set the arm down on the blank and begin recording. When done simply pick it up off the blank. It's possible to cut start/end groove manually with some home units but it's not easily done.