I think there is very clearly a bit of recognition of some kind there. I think thats very obvious. From a 1977 only POV, why would it be there? I take it to mean that Obi-Wan could recognize this specific droid. But it probably means he recognizes this "kind" of droid. And it being somewhat specific to war or fighting or at the very least, that it is a big time droid from the most serious parts of the galaxy.

Sometimes it seems like Obi-Wan has always been some kind of old timey not technologically advanced kind of guy. But he knows about droids. He says he doesn't seem to remember owning a droid but on the Death Star he busts out with "plug in. You should be able to get a blah blah blah" So he's quite familar with droids and Astromechs in general.