John
Dig into the Rutherford books.
I am going by memory but Jim did mention the 103 sometimes being a number for a Artist Proof.
I have seen the 103AP on ebay three times.
Also I think Jim said that some special numbers were made for friends of the family. My guess is that this full set was made for a friend of Youngers. I will have to go throught the RJ books again and double check this.