A Bombardon in Eb is an old name for an Eb bass or Tuba.
The Bb Basse is known a Contra-Bass on the same era of brass band music

As a 12- 16 year old, a few+ years ago I found that taking a bombardon on a tramcar or bus was a very anti-social activity. My education in bad and abusive langauage was completed at that time, from fellow passengers, conductors and especially from conductesses whose vehemence at the sight of a small boy with a very large instrument was to be heard to be believed.
I never understood why they were so upset! Those were the days *BG*
;>) Kenny B