It's not the broadest: the broadest is M3. Also, it's not true that it consists of assets that are not liquid.
The best answer is that it represents money that people have easy and immediate access to
It show that civilians had a understanding of astronomy
Navy, trade (second could be multiple things)
I believe it is the Sumerian.
Military presence
Self rule
Trade
Slavery / Mulados/ Creoles/ etc