Colcothar or rouge is a red oxide pigment used by clockmakers in the 18th century for cleaning and polishing brass. The Dominy clockmakers used it on long leather-wrapped wooden buffers which survive today in the Winterthur museum. Daniel Burnap discusses some uses for it in his 1779 memorandum book. 
Colcothar was also used as red pigment for red washing the interior of clock cases, undoubtedly with an oil base to prevent warping from the opposite veneered face. 
This includes one bottle (8 ounces) of true, historical colcothar rouge.