Most commonly known as 'OP' these were the rage 84-88 when i was at school. The T-shirts had 'OP' on the chest and a small or large print such as palm trees or ocean scene and usually, on the back, another print. Made for the summer... unless you're from Newcastle and then they are also worn in the "what do you mean it's cold? are you soft or something?" winter months.
They also made shorts. In fact they still do. And T-shirts. What are you waiting for? buy one for a relative this Christmas.