Upon closer examination they discover, with horror, that it’s coming from inside! They shatter part of the face and we see the left eye of the fear-stricken model inside (who has somehow miraculously survived.)

Also, if the production had a bigger budget it could have gone the “automated art factory” route where Walter builds a machine that allows him to produce hundreds of statues (a giant vat of clay!) which also serves as his ultimate demise.