Economy Class Seating On A Pan Am 747 In The Late 1960's (imgur.com)

Here's a real photo of coach from 1966--it's a 707, not a 747, but it looks much closer to today's commercial flight experience than the mockup.

http://www.calgaryherald.com/business/cms/binary/7939683.jpg

The original 747-100 /was/ spacious on international flights, the upper deck had a lounge and a piano. This wasn't due to some bygone era where passengers weren't treated like cattle, it was due to the underpowered JT9D-3A engines.

Without sufficient power, the airlines lowered the amount of allowed weight on allowed on international flights and thus the seats had better spacing. Later models starting form the -200 model had more powerful engines so they crammed in more passengers - both in coach and in first class.