I can give you a little bit of extra info on your field piece since I have two--one I built from a CVA kit and one that I bought pre-assembled that appears to be identical to yours. I think I got my finished model on EBay for about $350, which I thought a bargain at the time. If you only gave a little over $200 then you did get a steal. These sell new in the $550 to $700 range by the few sources that carry them and it's very possible that some company like Franklin mint may have sold them at some time. The kits for these models sold for around $150 to $175, but then that was a a lot more money in the 70's than now.
To the best of my knowledge the kits for these were only imported from Spain and marketed by CVA (Connecticut Valley Arms) back in the mid 70's, which was during the heyday of the black powder revival. It was marketed as the Napoleon III and the kit came in two sizes---a large model like yours, which was a 1/5 scale, and a smaller (probably 1/8th or 1/10th scale) version that was not as detailed and did not look as well proportioned.
Even though CVA marketed these as models of US civil war pieces they are actually models of contemporary European (French) field pieces--Hence the name Napoleon III, who was a nephew of Bonaparte and had the distinction of being both the president of the second French republic and a dictator of the second French empire in the mid 19th century. The ammunition boxes on the axles and the lunette assembly are also indicators of a European prototype rather than American.
CVA also marketed kits for a large 1/4 scale 12lb mountain howitzer and a smaller 1/8th or 1/10th version of the same. I have one of the large kits still boxed up waiting to be assembled. It has a steel barrel with a .58 caliber rifled bore.
Of course there were the Old ironsides cannons which were sold in both kit and finished form as were some of the other smaller cannons. I have two of these also--one I built from a kit, and one I found at a flea market for less than $25. Like you, I would not pay the $100 price tag that they bring on Ebay, but that seems to be the norm.
Most of these models are are marked as made in Spain and sometimes will also have the name Dikar, which I assume is the name of the Spanish manufacturer. I have seen a couple of spellings of this name, but I suspect in some cases it only appeared to be different because of poor or worn stamp engraving.
When the black powder reproduction market slowed down, CVA dropped all of the cannon kits and eventually the finished models also.
However, both the large and small Napoleons continued to be imported and sold as a finished models by a few outlets that deal in black powder items such as Dixie Gunworks and Cannonmania. They both still list these items for sale although they are sometimes out of stock.
The large "finished" Napoleons III's differ from the old CVA kits in a few respects. First of all the finished models do not come vented as you discovered. Secondly, the metal parts have all been nickel plated to prevent rust. Rust is a big issue with the old untreated steel used in the CVA kits, which is why one sees them all the time on EBay covered in rust and rust pits. Thirdly, the barrels on the old kits have a breech plug that can be screwed out while the later finished models appear to be machined solid. Lastly, the wheels on the finished models have a much deeper dish than the ones that came on the kits and the metal to wood fit is much better .
When I built my kit the tire rims on the wheels fit so poorly that there were large gaps between the wood and metal. I solved this problem by removing the metal tires and then laminating an extra 1/16 inch of similar wood to the circumference of the rim of the wheel. I then heat fitted the original tires back on for an authentic tight fit. The original assembly instructions for the CVA kits actually explained this poor fit away as replicating the crudity of manufacturing techniques of the period these pieces represented----which of course was a total load of bullocks since wheelwrights were generally experts at their craft and wheels for military use had to be made especially well to hold up to harsh conditions..
Hope that helps a bit.
P.S. I am making these observations on the differences between the kits and the finished models based on the two examples that I own. However there may be other variations
