(March 6): A lawmaker is calling for an investigation of a US$54.2 million, after-hours purchase of Oshkosh Corp. stock the day before the company won a blockbuster contract to build trucks for the U.S. Postal Service.

The transaction of 524,400 shares is bigger than Oshkosh trading volume for some entire days. The block itself amounted to almost 1% of the company’s publicly available shares and 74% of the firm’s 20-day average volume, according to data compiled by Bloomberg.