Read the passage below:
[1] For decades, art historians attributed the anonymous architectural sketches of the Hague Municipal Archive to the circle of Jacob van Campen based on stylistic affinities in draughtsmanship. [2] However, recent beta-radiographical examinations of the laid paper's watermarks have challenged this long-held attribution by revealing a paper maker's mark that was not produced prior to 1665. [3] Because Van Campen's influence in The Hague waned significantly after his death in 1657, scholars had previously assumed these drawings were executed during his peak productivity in the 1640s. [4] The physical evidence instead demonstrates that the sketches were created during a later period of civic renovation, thereby undermining the stylistic argument for Van Campen's direct oversight. [5] Consequently, curators must now re-examine the role of lesser-known local master builders who directed municipal projects in the late seventeenth century.
Select the sentence in the passage that introduces empirical physical evidence that refutes the traditional chronological assumption regarding when the drawings were produced.
Answer: However, recent beta-radiographical examinations of the laid paper's watermarks have challenged this long-held attribution by revealing a paper maker's mark that was not produced prior to 1665. / Sentence 2 / [2] / recent beta-radiographical examinations of the laid paper's watermarks have challenged this long-held attribution by revealing a paper maker's mark that was not produced prior to 1665.