The effects of prior encodings of manipulatives (red and blue plastic chips) on children's ability to use them as representations of quantity were tested. First graders (N = 73) were assigned to four conditions in which the encoding of plastic chips was experimentally manipulated. All children then participated in an addition activity that relied on the chips' quantitative representations. Children who were given quantitative encodings were better able to use the chips with meaning relative to those who played with them during the encoding phase. Children who perceived the chips as toys after encoding were similarly hindered on their ability to use them as quantities. The findings suggest that prior encodings are predictive of children's quantitative representations of manipulatives.