A Matross was the lowest rank in the Artillery and the term for a Private in a train of artillery (a gunner's mate). One of the soldiers who assisted the gunners in loading, firing, and also sponging the guns to stop them overheating. "They carried flintlocks and marched with store wagons, acting as guards" 
In muster rolls, Matross was generally the term used until about 1800 when the term Gunner also started to be used. The term matross discontinued in about 1820 and from then onwards only the term gunner is used.
One of the meanings of the term Classy, or Clashy is Matross.
Historical books online
- "Matross" pages 562-563 Hobson-Jobson: being a glossary of Anglo-Indian colloquial words and phrases, and of kindred terms; etymological, historical, geographical, and discursive by Henry Yule and Arthur Coke Burnell. New edition edited by William Crooke 1903 Archive.org
- A Tug on the Thread by Diana Quick pub. 2009
- "Classy, Clashy" page 223 Hobson-Jobson by Col.Henry Yule and AC Burnell. New edition edited by William Crooke 1903 Archive.org