There are actually two different number series of the 13-inch discs,
and two tuning scales, even though on the table-top machines that
I have seen both types will play the "wrong" type and sound terrible,
of course.

Full details are in my book, "The Disc Musical Box," reduced in price
here in Europe from UKP 70 to to UKP 55 plus postage.

Thanks,
Kevin McElhone