This is purely a guess. There are 9 men who are "Members of Mark Club" buried between 1800 and 1809. It could be a form of Burial Club which covered the costs of the burial. The Vestry Minutes might refer to it. There is no mention that I can see in the book "Mark, A Somerset Moorland Village" by Pamela Slocombe.
David Boley has pointed out to me that on Page 355 of Pam Slocombe's book there is a paragraph about the Mark Friendly Society, which might have been known locally as the Mark Club. If anyone has family papers which mention the Friendly Society I'm sure that he would be interested. It was mentioned as late as 1865 in the Western Gazette when it met in the Pack Horse Inn.