I recently found my old, beat-up Mattel X-15 tricycle in my parents attic. It was given to me as a birthday gift by my grandparents when I was about 5 years old. I rode it for several years. I wish I knew how many miles I put on it but I bet it was a lot. I was probably the best gift I ever received. I decided to restore it.
I took it completely apart and sanded everything down to bare metal. Then I had Sherwin Williams match the paint from a patch of pain on the inside of the body. It cost me about $45 to have the paint made and put into spray cans. Then I remade all the decals digitally and printed them on sticky-back photo paper. After painting the body and wheels with primer and paint, I applied the new decals and then applied several layers of clearcoat over the top. The tires were cleaned up as best as able with several different chemicals. The v-rroom mechanism was in reasonably good condition but required remaking a couple parts. It now works virtually like new with the cool v-rroom sound when the front wheel turns. The seat belt was old and brittle so I remade it with a piece of rubber from a skin diving belt. I polished up all the chrome and hardware.
Overall it turned out pretty good. I have it displayed on my basement wall with a couple old pictures of the original Mattel advertisements.