Thanks everyone. The paper was onion skin, and is very creased and yellowed, and the pencil lines were all quite faded. I had to process them all in Photoshop for them to be legible. I have hundreds of these old blueprints, I'm posting one of the old drawings a day to http://starshipdesigns.tumblr.com/
. Check them out for a taste of '70s fan nostalgia. Maybe sometime soon I'll pull out the old t-square and angles again and see if the old version of myself can do better than my kid self.