I don't know how much you know about the procedure, so don't think I'm patronyzing you.
First, this is an older case file. If there is some way you can narrow down the time-frame, that helps. "Around" 1955 may extend to many years (from personal research). If they were residing apart for a period of time, that also makes the time frame larger.
A Divorce or Dissolution is a civil case and is public record. Whoever initiates the case with a Petition, is the Petitioner, the other party is the Respondent. It is filed in the Superior Court of a county. In this case, if "could" have been filed in either Fresno County, or San Bernardino County, OR any county in the State or another State. A large number of people in Washington State file in Davenport, Adams COunty, due to the low cost and fast turnover. The Petition is the first document filed within the Superior Court Clerk's office. It is given a case number (the number types vary by court) and a title, such as: "Charles P. Miller, Petitioner; versus Geraldine Miller, Respondent, Dissolution. Every additional action following is so filed. The original filing is recorded in the "Big Book" (usually the procedure across the land). These books are usually Red in color, about 24 x 36 inches. They have handwritten entry on the date of origination (Petition), the parties involved and case type. Unless there is a microfilm index, this book would have to be reviewed.
Court Clerks are required by law to maintain court records. This 1955 case may not be still filed on hardcopy, but on microfilm, microfiche. I would bet the original file is still in hardcopy. Some Clerk's office will obtain the records and make copies of those documents within the case requested. I don't know what total information you are seeking, and that would make a difference as to what documents to request. The original petition is usually a good request. The final dissolution is usually a good document. The final dissolution doesn't really say much except the marriage is dissolved, what support payments are to be made, how possessions are to be divided and how debts are to be paid. If there were children, there is usually a statement that child care/support will be followed as to requirements of a different document concerning the children (custody, visitations, support, who makes the decisions for medical, etc).
I would suggest you call each Court Clerk's office to ask if they do the research and how much cost. IF they do, there is the research charge, the charge to copy each page requested and mailing/handling, etc. If they do, I'd first ask to receive just the case "Docket." Then you can decide what filings you really want. Many filings are lawyers asking for continuance due to vacations, etc. You won't need the filing saying the Respondent received notification/
summons. If this was a quick case, both agreed, no children, there may not be many documents. If she fought it and they had to have witnesses, court records (abuse, etc), it could be lengthy.
This PDF indicates the clerks office WILL do the research, para 10:http://www.sb-court.org/Portals/0/Documents/PDF/General%20In...
No real online information as to old records or clerk help.