context: In the final stages of construction, work stopped for two months with the PIK team taking part in the Spanish Sailing World Championships in the summer of 1952. At the same time, Lounamaa moved to work in Tampere, and the management of the project was left to Mellén. Later in the fall, the final letter was issued, after which the prototype was completed after four years of work and 3,500-4,000 hours of work in January 1953. The final setup was made in the freezing 20 degrees Celsius, and after that it was noticed that the focus shifted too much due to a more powerful but heavier power unit [2], which caused Tumppu to crash his nose in the test runs already at partial engine power.
question: When was the Tumpu prototype built?
answers.text: in January 1953