An intact iron and copper-alloy canteen of military type found in a 4th-century site in Gaul - http://www.thehistoryblog.com/archives/58325
Wow! New to me. Sets off various trains of thought... all under the heading ritual.
Very interesting. I'm not sure by what they author means by a "padlock." I enlarged the three photos in the article and I only saw what might have been a "leash" to prevent the stopper from being lost, or perhaps a tie down device to keep the stopper from working lose and spilling contents.
Since legionaries had the cost of their equipment deducted from pay or pay for it out of pocket, I was wondering how much a canteen would cost. It doesn't seem to be cheap considering its construction and materials. As a temple offering, it could be a significant expense for a soldier. Perhaps as a prayer for protection before a campaign, or as a thanksgiving offering after a campaign.