I picked this canteen up a few weeks ago. It's a standard Pattern of 1862 Federal canteen marked "J. HALL ROHRMAN PHILAD." on the spout. It has the same brown twill cover and remnants of the white tape sling seen on most surviving examples of Rohrman canteens I found online. What makes this one especially interesting are the markings.
It's difficult to make out, but one side seems to be inked:
Co. A. V.R.
The other side is marked:
[Illegible, but appears to be a name ending in "LIM"]
Co. A V.T.
I wish I knew more about the provenance or could at least make out the markings better. i don't know if it's trying to say the same person used the same canteen in the Civil War and Spanish-American War (barely possible), or maybe two different family members used it in two different wars. Or maybe something else entirely.