A borrowed money from B and orally agreed that B had a security interest in equipment that

Question:

A borrowed money from B and orally agreed that B had a security interest in equipment that was standing in A’s yard. Nothing was in writing, and no filing of any kind was made. Nine days later, B took possession of the equipment. What kind of interest did B have in the equipment after taking possession of it? [Transport Equipment Co. v Guaranty State Bank, 518 F2d 373 (10th Cir)]