Convert from button measure to pace [great]

Unit Definition (button measure)
The button measure is a unit of distance equal to 1/40 inch (0.635 millimeter), used to measure the thickness of buttons.

Unit Definition (pace [great])
A pace (or double-pace) is a measure of distance used by Ancient Rome. It is the measure of a full stride from the position of the heel when it is raised from the ground to the point he heel is set down again at the end of the step. In Rome this was standardized as about five Roman feet or 58.1 English inches.