Nice find, a first see for me.
Master Marble Co did not have a huge variety of marbles, so guessing at nice Sunbursts would be my way.
Master had their own “Game Marble” boxes so I would doubt that gamers came in your box.
The bag is generic imho, are you sure that a bag was included?
Check the bottom of the box for marble roll marks, it may have been a fully filled box.
Nice Find!!
Marble—On!!