Monika Jaskólska, who is coordinating the charity drive, put the car on display in Bielsko-Biała, southern Poland, on Monday.
The Syrena 105 is due to be auctioned next year during a charity ball organised by Jaskólska’s foundation It Pays to Help Out, Poland’s PAP news agency has reported.
Jaskólska said: "People are already interested in the purchase, so we wanted to show them [the car] today.”
The proceeds from the ball and auction will go to a pediatric hospital in Bielsko-Biała.
Jaskólska said: "We support this facility and its children's psychiatry ward.” She added: “We would like to create a nationwide campaign concerning children’s mental health.”
The car was manufactured in 1980. Following the renovation, the vehicle is now fitted with an original 40 hp engine.
Daniel Kasprzyk, a mechanic from BB Oldtime Garage, said: “We took apart [the car] to the last screw and put it back together using original, unused spare parts.”
The Syrena will now be sent to a repair shop run by the Collins brothers for tuning. Rafał Collins said: "Our role is to add a little personality, individuality and a little heart to the car.”
Tom Hanks began collaborating with Jaskólska after she initiated a fundraiser to buy and renovate a vintage Fiat 126p and gift it to the American actor in 2017.
The extra money left after the purchase of the car went to the pediatric hospital in Bielsko-Biała.
Hanks later declared he would buy and finance the renovation of the Syrena, which would then be put up for auction.