Complex sentence: Martin has been collecting baseball memorabilia since 1975 his collection is a time line of baseball history in equipment and memorabilia consisting of over 2,000 items dating back to the 1850's.
Split into simpler sentences: Martin has been collecting baseball memorabilia since 1975. His collection is a time line of baseball history in equipment and memorabilia consisting of over 2,000 items dating back to the 1850's.