Thanks.
I don't know about limits but I guess there were no printing limits. There used to be this thing called "first bits" which I think was case insensitive, maybe these addresses are generated on that basis.
In the "more info" link above, there's a list of all v0.1 coins, #20 being:
#20 16b8qam 16B8qAMR1d6Q1TAQmcVWBpKV5xGuYQvU88