In this episode the Thai 1911s were described at 410 gauge - I think they are actually 12 guage!
https://homemadeguns.wordpress.com/2014/12/09/pen-guns-and-various-homemade-pistols-seized-in-thailand/
http://www.thefirearmblog.com/blog/2015/03/06/shotgun-1911-from-thailand/
https://homemadeguns.wordpress.com/2014/12/09/pen-guns-and-various-homemade-pistols-seized-in-thailand/
http://www.thefirearmblog.com/blog/2015/03/06/shotgun-1911-from-thailand/