Mule Deer's comment is correct, as are roundoak and irfubar (sorry if I missed anyone else). Here is O'Connor himself in his book, The Big Game Rifle published in 1952:
"As I write this I have just finished sighting and tuning up a beautiful little mountain rifle which was custom made to my specifications. Tom Burgess, East 823 Sinto Avenue, Spokane 13, Washington, did the metal work, fitting a light 22-inch 7mm barrel to Czech VZ-24 action. He altered the bolt handle for low scope mounting, thinned it down to neat and graceful lines and saving a little weight. He streamlined the trigger guard, hinging the floor plate and put a quick release button on the forward part of the guard. He fitted a Dayton-Traister trigger and Sukalle safety, mounted a Weaver K-4 on the Buehler top bridge mount. Russ Lenoard, also of Spokane, made a trim and handsome stock for it, beautifully shaped and needed."
Note that the VZ-24 is a large-ring action, which is what is shown in irfubar and roundoak's posts.
And much later, in the Gun Digest 1974 article "Forty Years with the Little 7mm," he wrote, "Before long my wife latched onto it. I had the stock shortened and a recoil pad installed. This 7x57 has been her favorite rifle ever since." The article also includes a photo of said rifle (see irfubar's post) with the caption, "Mrs. O'Connor's 7x57 Mauser, metalsmithing by Burgess, stock by Russ Leonard. Shown here with Buehler mount and Weaver K4, but it now carries a Leupold 3x."
