Hi Mark and Fernando,
First of all I guess that the seller thought that barrel was Austrian because unbelievably large numbers of these are still around in both Bavaria and Austria, where they are often employed as door stoppers in old houses. Forget about his tentative dating 'ca. 1750' though.
I attach the images for documentary purposes as they will not be around on Ebay for too long.
Secondly, Fernando is perfectly on the right track and made the final note by pointing out that the barrel was staged and the heavily swamped flat muzzle section would make an ideal land mark for the fore end of a stock.
Thirdly, before probably being around as a signaler and door stopper for two or three hundred years that barrel was definitely stocked and used for 'serious' purposes at the earlier stages of its working life which may have started as early as the 1440's!!! The small touch hole near the rear end and the large, flat muzzle head perfectly fit that Hussite Period.
Something very rarely found on early wrought iron barrels are the hammered longitudinal decorative grooves between the edges.
I include a scan of a similar barrel retaining its original stock and looped hook, now preserved at the Czech Military Museum in the Hradčany Castle Prague.
Best,
Michael