Complex sentence: From 1956 to 2006 the Bourne Society published a newsletter, "The Bourne Society Bulletin" that eventually developed into a quarterly publication, of which 202 issues were produced.
Split into simpler sentences: From 1956 to 2006 the Bourne Society published a newsletter, "The Bourne Society Bulletin". This initially appeared in an ad-hoc fashion but eventually developed into a quarterly publication, of which 202 issues were produced.