Well this is sort of intriguing, even for someone like me who knows little or nothing.
I'm going to try to be 'sleuthy' here, because my buddy Steph likes sleuths and even
if I fail miserably she'll admire the effort.
Just realized that Jessica already beat me to my first thought. All we have here are
three letters, so the ass-umption of 'maker' is jumping the gun a little. (Didn't mean
the funny word as an insult. I've made more of these than you ever will!)
My second thought was what do you mean by "some bags of"? Is this potentially relevant,
as in traditional marble pouch bag, or packaged mesh/net bag? Or do the marbles just
happen to have been placed in bags at some point and we can skip that detail?
My personal ass-umption is that MAD is a fairly 'broad' categorization in one sense, given
the other pretty wide-ranging descriptions. But it probably has at least one very specific
component to it.
Since I've already bored everyone to tears. let me make one hypothesis.
If MAD turns out to be "Marble Alan Something", that might be pretty interesting. ( :