William J Mason did indeed serve with Francis Marion West and was captured Bloomfield Iowa. Sent to Alton. Survived war.

https://books.google.com/books?id=qLZWpI8ayTIC&vq=mason&pg=PA1352#v=snippet&q=mason&f=false

History of NE Missouri (Williams) Vol 3 pages 1351-1352

see also: https://www.sos.mo.gov/Images/Archives/Military/s00735/s00735_2270.pdf

JJR