Detailed Instructions: Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
Q: The TK (also known as the TK-3) tankette was a Polish design produced from 1931 based on the chassis of the British Carden Loyd tankette, with an improved hull and more powerful engine, and armour up to 8 mm thick (10 mm on the TKS).
A:
What year was the service entry date for TKS?