The "Original 7" Mercury astronauts only had the NASA insignia on their spacesuits and nothing else. They were permitted to personalize their flights by naming their space "capsules" as they were referred to in those days. There was no project patch for Mercury as there was for subsequent projects. The patch above is a souvenir version that was made after the Mercury project was over. It shows the astronomical symbol for the planet Mercury and the number 7 honoring the "Original 7" astronauts. Several more souvenir patches for the Mercury project were designed.
Below, you see a picture of the Mercury monument at Cape Canaveral.