You can find the value of a silver-plate tea set by contacting an appraiser who specializes in such items. Furthermore, you need to make sure that the appraiser belongs to a respected organization such as either the American Society of Appraisers, the Appraisers Association of America or the International Association of Appraisers. This way, you can be sure that the appraiser has both the expertise and the experience needed to provide you with a fair and accurate assessment.
If you are unwilling to contact an appraiser, you have two other options for finding the value of a silver-plate tea set.
First, you can look up similar items as listed in the price guides. The more similar the tea set and the more similar the condition to something listed in them, the more similar its probable value. However, please note that even small differences in the items can lead to big differences in their value, meaning that this is not a reliable method unless you are an appraiser.
Second, you should check your local auction houses, which are sometimes known to appraise the items that interested individuals bring in. In rare cases, they might even be willing to do a long-distance appraisal of your silver-plate tea set by looking at a photo.