Historic letters

I have 6 letters from the 1920s-1930s that I am going to cite.  These are on business letterhead and are letters of recomendation not addressed to anyone in particular. My grandfather worked as a cooper.  The letters from his employers stated he did good work but had to be let go because there wasn't enough work for him to do. He worked for periods of time then on to the next employer.  He worked for one of the employers 4 different times.  These letters put my grandfather at a specific place at a specific time not to mention in the early ones he was an apprentice, later a journeyman and then a cooper so the contents of the letters are important.

The problem is, I am not sure how to word who the letter is to because it isn't to anyone in particular. Here is where I am at.

Richard Schütze (Luckenwalde, Germany) letter of recommendation for August Weichert, 20 April 1929; privately held by Michele Simmons Lewis, Harlem, Georgia, 2003. This letter was in the possession of August's son Karl until Karl's death in 2003. At that time August's daughter Emma took possession and then passed them to Lewis (Emma's daughter).

I am also thinking I could word the provenance a bit better?