[fernando]

Thank you Gene,
According to what i have observed in the mean time, there certainly are quite a few variations of these things, which makes a specific specimen be only identified against a rather similar item, or by someone who has seen ( or handled) so many of them, that he would feel safe to put a label on it.
In a way, the volume of this example seems not so distant from the ones of primitive hand cannons, like the Switz arquebus shown in your link. But then we would be talking 14th century, which decidedly is not the case here.
On the other hand, this to be a signal cannon, spreads within a family that gave the so called thunder mugs, which in implies in powder testers, saluting and also signal cannons. I have meanwhile seen pictures of "later" thunder mugs ( 1800's) and they were all more sophisticated, like some examples having a lip below the firehole for placing the charge ( no fuse in this case), other times a carrying handle and, most often a wider rimmed base, to keep the thing well upright.
So if in fact this is a signal (saluting) cannon, which untill contrary evidence i beleive it is, its rudimentary shape fits into the age atributed by the seller, XVI/XVII century.
By the way, where did you get the picture of this last example you showed ?
Fernando