My only dated ceramics were made during undergraduate work at the College of Wooster in Ohio, from 1966-68. Those functional pots are exclusively made of glazed earthenware and initialed "WCH."
My earliest stamped mark. A large Baskerville ampersand. It was used during my graduate program at The Ohio State University from 1968-70.
A drawn "H" used from 1970-72 while teaching at Valley City State College in North Dakota.
A lead type letter "H" used from late 1972 until approximately 1980 in Columbus, Ohio, while at Ceramics Monthly magazine.
This stamp (W topping an H) was used on work made at the Archie Bray Foundation in Helena, Montana in 1996 when I started making ceramics full-time after leaving Ceramics Monthly.
Tiles made at the Archie Bray foundation in my 1966 residency were marked like this.