Armament rating

A armament rating was a rating system assigned to all spacecraft based on both the offensive and defensive weaponry of a given ship. Factors that helped determine the rating were the type and number of weapons, the maximum firing range and power output capacity.

Generally accepted ratings were:
 * 0 - No weapons
 * 1 - Light defensive weapons only
 * 2 - Light defensive and offensive capability
 * 3 - Medium defensive and offensive capability
 * 4 - Heavy defensive and offensive capability

Source

 * A Guide to the Star Wars Universe (Third Edition)
 * The Star Wars Encyclopedia