What is the purpose of this braze-on?
My thinking is that it is a brazed on guide for dynamo hub wiring. A touring bike like the Devinci Caribou would likely have provisions for things like dynamo lighting (I think that it'd be more likey that this was the case than someone erroneously adding a disc brake cable guide on a non-disc fork.) Typical braze-ons look like this:




As you can see there are a few different types. Some look like brake housing guides while others are unmistakably for flexible wires from a hub generator. As per the question of whether dynamo hubs have wires on one side or the other, I searched through Peter White's endless information on dynamo lighting and learned that:


  If you have an older SON28 hub with a black painted center section, SONXS, SONXS100, SON20R or SONdelux it makes no difference which way you align the hub in the fork. And with the new SON hubs from 2012, you again have the freedom to place the hub in either orientation. The conectors can be on either side of the bike.


This is just for Schmidt dynamo hubs, but I'd imagine that there are examples elsewhere.