I agree with Lloyd that the gray one appears to be stone. And the first does look Akro/Master-ish
Steph, Your thoughts seem reasonable. I have seen many translucent agates that children could easily have referred to as moonies - some whiter and even more moon-like than this one. If, as you say, people were referring to moonie marbles before glass marbles were produced, such agates would seem to be top contenders for the monicker.