This question, although common, highlights one of the clear differences between the revaluation appraisal process and the more well-know "bank" appraisal. Most homeowners have had a "bank" appraisal on a property before and are familiar with the process involved and the resulting report. Many assume that the revaluation company uses the same process. Although the appraisal concepts are the same and the results similar, the process is different.
To answer this question it is important to understand that in a revaluation, the value of your property is based on an analysis of the entire real estate market for a specified period of time before the completion of the revaluation project (a one or two year period). This study of recent property sales allows the appraisers to establish valuation parameters (construction rates, land rates, market adjustments, etc). Ideally, when these valuation parameters are applied to the properties that sold, the calculation will result in an appraised value that is very close to the sales price.
The appraisers are required by the State to test that the parameters being used are consistently producing values that closely approximate the sale prices across all types of properties throughout the town. When this is accomplished, the appraisers can then apply these same valuation parameters to all of the "non-sale" properties in the town. In doing so, they are approximating the market value of each property using the information derived from all of the sales. Therefore, no particular sale or group of sales was used to determine the value your property. This is because ALL of the recent sales were included in the analysis that set the parameters used in the revaluation of your town.