Oil investment research company, legit or not

Hello, we are new to this. We are from MI. We received a letter from a Dakota Oil Investments and Research Company, Inc. It said they found some shares my late father in law had and said they can try to recover any payment, from 1981 forward. They want my husband to sign a contract they sent and sign a W9. I Told him not to sign anything because I cannot find company anywhere on internet . They want a third. But sounds shady to me. Supposedly located in Alto, MI