Often the min/max credit limits are published in the Credit Card reviews at Cannex:
Product Snapshots
For the Altitude Cards, the limits are:
Altitude Std : $1000 - $50000
Altitude Gold: $5000 - $50000
Altitude Plat : $10000 - $65000
However these are only a guide. Even though a card has a minimum and max credit limit, a bank often will allow a cardholder a higher limit eventually with a card (and sometimes start a card with a lower amount than the base credit limits)