Two cotton/poly knit fabric t-shirts, makers unknown. Click for bigger.
Here's two more excellent examples of the short-lived "word knit" trend of the 70s (previous example here).
I love striped t-shirts and "surfer shirts" from the 60s and 70s. They're usually easy to spot in thrift stores, but you've got to scan thousands of bland shirts to spot just one winner. The best ones tend to come from lower-caste department stores.
A really good patterned t-shirt can be a great alternative to wearing a tie.