We wish this was an easier topic than it is. We see hundred of folks a year who just need to replace an old broken/damaged/undesirable valve handle. The metaphor we fall back on a lot is it's kind of like replacing a 1920's carburetor - the part if different from manufacturer to manufacturer and time period to time period. Some companies, notably Chicago, have only a few different types of splines while some have many more.
A spline pattern refers to the shape of the mounting area at the base of the handle, like this:
Here there are the number of splines, or tiny ridges inside, as well as the width and sometimes the depth. This part can also be square,
Additionally, most handles have a set screw either down through the top or from the side. A small minority use a compression system with a nut that screws down:
All these variable have to align to get a proper replacement handle.
But! Don't lose heart! We have a sizable selection of handles to choose from in our store.
The best thing to do is bring in your stem (the part the handle fits on to) and we can test out different handles. It is nearly impossible to eye ball it, so a test piece is almost always necessary to ensure a match. If you can't bring in a stem, bring in a working handle and we can find a stem first (this will add to the time though, be advised!)
We know old plumbing can be tricky and time consuming, but we hope Hippo's resources can be of help!