Faceting resembles the facets on a gemstone (thus the word faceting) usually way les but still faceted. There are 3 types of terminations to where the cane was cut or (terminated) while forming the marble. "Faceted" i.e. the oldest type : melted pigtail : & unfinished. Faceting was accomplished by "grinding" the end down, creating the familiar "flat spots" of "faceting"
Melted pigtail, sometimes the pigtail is so obliterated (melted) that it will be barely visible.
Faceted : not a very good pic but the best In could come up with, you can see one of the "facets" visible near the upper center right hand side. I don't know how good you screen is but a few other facets are visible to me in this pic.
Both ends are "unfinished" on this Joseph Coat, I estimate the manufacture date my handmades using this, that and the colors are usually far brighter on the latter. Faceting was mostly done away with by 1870-1880, the higher demand for "gameboard" marbles in the late Victorian era made for much smaller sizes and the quicker production method of the unfinished ends.
Faceted on one end and a melted pigtail on the other usually indicates a manufacture date of between 1850-1870 or thereabouts.
Later manufacture (1870-1910,15) usually showed a great reduction in size along both ends being unfinished (quicker production) & brighter colors, these marbles were also often called English, though they were produced in Germany for the "English" gameboard market.