A Krupp C73 cannon.
As used by the Chinese Regular army and the German army.
This was used by the German Cavalry, hence seat at either side of barrel and foot rests.
[painted example and 28mm figure for scale.]
pdf added, hope it makes sense but check photos it really is quite easy to put together.
Mart is doing a Chinese crew for this at the moment and Mark will be making a German crew later this year.