Real mortar/parapet gun/cannon or ?

[M ELEY]

http://cgi.ebay.com/ws/eBayISAPI.dll...m=360145891147

I wanted to bid on this piece so bad, but there were just a few red flags with it. I think there might be parts to a real cannon here, but I'm not sure where the real things start and the others end?? Notice it comes from S. America. Possibly a late 18th c. piece refitted for the Industrial Revolution late 19th with the machine-made threaded bolts. Is that some sort of bolster? i regret passing on it now, especially since the gent that got it only paid what he did- less than what you can get a signal cannon for. Opinions on authenticity? Age? Port of origin? Use at sea vs a fort gun? Odd construction? Thanks.