For what its worth, picture No. 2 on the following website shows that the Nato 58 canteen (at least the one pictured) does not nest in the Crusader stainless steel mug. http://www.cardinalgear.com/crusader-cup-canteen.html

However, other pictures on this same website show other Osprey 58 canteens do nest in the Crusader SS mug.

Had I been to this website before I purchased the Nato canteens, at least I would have known what questions to ask.

Can anyone suggest a forum where this type of issue is discussed? Obvious interloper here.