Unfortunately I've not been able to find much information about this bag, but it is really cool.
At some point it was clearly PROPERTY OF THE FBI CLERK'S OFFICE, based on that being written inside the bag with permanent marker.
The exterior leather has split open along two outer seams, but the interior/liner is in really good condition.
The only tag inside the bag says "TOP GRAIN COWHIDE" with a "MUTUAL" logo on it.
The bag probably originally came from somewhere around Kansas City.
The base of the bag is about 14" x 20".
The height of the sides while open is about 10" but it loses a little height when it is closed.
EXTREMELY roomy -- kind of like a Mary Poppins bag.