At the end Jim discovers Dave Delaroux painted Beth's portrait over what Jim calls a "Federal Bearer Bond." A close up of the bond shows Dave Delaroux's name typed on it. Bearer bonds are called by that name because they are not issued to a particular person; whoever happens to possesses the bond (i.e., the bearer), is the legal owner of it, regardless of who the original owner was. They would never have the owner's name typed on it as that would make it a regular bond. Several years after this show bearer bonds were made illegal in the US for the very reason used in this story: it made for an easy way to launder money and smuggle it outside of the country.
In Rockford's trailer, Beth explains that Dave Delaroux is a "comptroller" for a company. But a comptroller manages government accounting, a "controller" is involved with private company finances.
After Rockford smashes the jar of blue paint on Dave Delaroux's car windshield they get in a fight. Fresh blue paint is clearly visible on both of Rockford's knuckles. During their struggle Rockford grabs Dave's shirt, his coat, and slugs him in the face, but no blue paint shows up on Dave anywhere.