C.E. Heyer was awarded a design patent for Clematis in 1884–1885 [USPTO D15684]; he assigned the rights (by name) to Arthur M. and Alson E. Barnhart of Chicago, his employers since 1878.
The earliest examined commercial specimen is shown in The Inland Printer dated March 1885. BBS offered it until 1900 (perhaps later), and it was distributed by at least two other TFs.
While engaging the device of a dainty floral theme, Clematis exemplifies Heyer’s strong “hooked C” of Emerald, patented in 1881–1882, Eclipse (1882) and later designs.
This distinctive curve is an exaggeration of the one for Copley# (Boston TF ≤1877). Perhaps Heyer recalled it from his years in Boston, where an anonymous sign-painter created the model for this spectacular stylized roman.