[Child of the 7th Age]

I don't have a 1930s Hobbit--that would be really rare. But I do have The Annotated Hobbit which was published in the 1980s and this contains both the old and new versions of the story. Also, there is a book called A Tolkien Compass edited by Jared Lobdell and this has an essay called "Gollum's Character Transformation in the Hobbit" by Bonnie Jean Christensen. I can't put my fingers on the Annotated Hobbit right now because it's in the back of the house and my entire family is sleeping, and they will kill me if I wake them! But I do have that essay here. This is what Christensen says (paraphrasing)--In the first edition of the Hobbit, Gollum is a "lost soul" who would kill but who would not violate his oath. He freely offers a ring as a prize to Bilbo in a riddle contest. When he loses and is unable to produce the ring, he courteously shows Bilbo the way out of the mountain. By the second hardback edition, Gollum is a withered, totally depraved creature dominated by an evil ring and capable of any crime. In the 1966 edition, there are even a few more changes to stress Gollum's depravity.

Most of the changes between the early ad later editions come in the second half of the chapter. It doubles in length. The first change in the chapter involves the prize--the newer version substitutes help in finding a way out in place of the original present of a ring. The essay gives a line-by-line comparison between the original edition and the later one. The later edition describes the ring as a "ring of power" which the early edition does not; they just say it's a magical ring. In the first edition, Gollum is much nicer. He goes to look for the ring in his treasure trove and when he can't find it (because it's in Bilbo's pocket!), Gollum even offers "to catch Bilbo some nice juicy fish to eat as consolation."

In the first edition, there is no scene where Bilbo stands next to Gollum and is invisible because he has the ring on, and then feels pity so doesn't kill him. This was added for the later editions so it will tie into the whole theme of pity and mercy in the LOTR. Also the first edition doesn't have the scene where the angry Gollum chases Bilbo down the passage shrieking his anger at him; this is only in the revised edition and again ties into the themes of the LOTR when Gollum chases Frodo and Sam wanting his ring back.

The essay doesn't say anything about Bilbo's explanation to Gandalf about how he got the ring. If I have time, I'll check the Annotated Hobbit tomorrow and see if there's anything else. Oh yes, I think they are revising and reprinting the Annotated Hobbit later ths year. I saw something on amazon.com. It is a really nice book, much large than the usual Hobbit and with many pictures and explanations in the margin.

I'm not sure if this really answers your question, but it does show how major the changes were between the two editions. And all of it was done to tie Gollum, the ring, and the theme of pity into Tolkien's "new" book, the LotR.