Actually , IIRC , in the '60s sales , you could buy a " serviceable " carbine for a price . It would be pulled and inspected . If it was bad , another would be pulled in it's place or repairs made . This would take time , and time was money , so the price was higher .
You could also choose to buy an " unserviceable " grade for less , which was just pulled , given a quick eyeball , and sent out . It could , and most times was , as good as a serviceable one , but there were exceptions .
Chris