I've been after a similar canvas pack, without spending Duluth type money. The wynnchester site has some nice reconditioned 50's Swiss canvas leather ruck sacks that caught my eye...BUT THEIR PRICES ARE CRAZY.
If anyone knows the actual model of the vintage ruck sacks in the pics below so I or anyone else could buy and recondition myself, I'm sure it would answer the OP's question (and mine)
The first one has a roll too which I find very attractive as you can alter the pack size.
The second one is more conventional but just as nice.... Just not £150 nice when they probably cost &10am as surplus, I realise some effort went in to em waxing and feeding the leather but nothing anyone couldn't do surely.
Any input in the models of ruck sack? I've got an LK35 but way something a bit more rustic
Hope this has been of some help to the OP.
Luke