There are a number of possibilities for the origin and vintage of the canteen. One key detail of your canteen is the sheet steel tin-plated spout. Authors and collectors have created much discussion of the standard pattern sheet steel tin-plated spout canteens supposedly contracted by the Cincinnati Quartermaster Depot during the American Civil War. I'm not so sure that this spout construction is necessarily exclusive to Cincinnati Depot contract(s) but suffice it to say that a relativity small percentage of the canteens manufactured during the Civil War had sheet steel tin-plated spouts. Most of the canteens manufactured to the pattern canteens in the depots had pewter spouts. Speaking of the pattern canteens they were consistent in shape in that both sides were uniformly convex and your example appears to be originally constructed with flattened sides not consistent with the standard pattern Civil War contract canteen.

This brings up the possibility of manufacture on a state contract. In the first year of the war several of the states provided their three-month volunteers with canteens and other accouterments locally manufactured. Canteens of unknown origin similar to the standard federal pattern have been attributed to state contracts. The early issue of the canteens, and relatively small number manufactured, and survival rate of these canteens suggest very few examples exist and without provenance remain unidentified.

In the course of research I have noted that at least two companies reported in correspondence intended to solicit contracts to the Ordnance Department in 1898 that they were manufacturing canteens to military pattern. There is no description or images of these canteens so I can only suggest that your canteen was possibly manufactured for commercial sales in the late 19th Century. At least one of the contractors that manufactured canteens during the War with Spain 1898, manufactured canteens with sheet steel tin-plated spouts. These canteens were assembled with the standard triangular wire loops and double covered with wool petersham and duck covers so are not consistent with your canteen, but does demonstrate that sheet steel tin-plated spouts were still assembled to canteens in 1898.

I occasionally see similar canteens attributed to foreign military service that may also be the source of the canteen, but I don't recall seeing an example with the three strap loops assembled to the canteen and some of the examples shown were porcelain-plated so are not consistent with your canteen. All this suggests a number of possibilities, but to state without equivocation by whom, where and when the canteen was manufactured very difficult to determine.

An image of a canteen similar to yours is illustrated in "Civil War Canteens" Silvia and O'Donnell, 1983/1990, p. 135 with the comment, "Tin oblate spheroid canteen (approx 7 inch diameter) with a tin spout, brown woolen cover and a standard U.S. sling. We have seen quite a few similar specimens, often with Federal provenance, although these have flat faces and are too small to be considered variants of the Model 1858. We suspect these were commercially available during the war and possibly purchased by several state militias."

I rather doubt that you will find anyone, lest of all on this forum that can provide you the definitive answer you seek.