Looks like a nice one! The blade doesn't appear to have been re-profiled, or even sharpened to the point of being noticeably short, and I can still see the original glazing on it. If the rest of the implements are in similar condition and the "walk and talk" is good all the way around, I'd say $150 on a slow day and $225 on a good day. Some collectors will pay more for the red scales, too, and 1964 was the last year it was standard specification for this model although they appear as late as 1978. I've noticed lately that these Model 1961's seem to command higher prices in some European countries than the US, especially the early ones.
Edit -- I didn't answer your question about rarity. 62-64 are definitely less common than than 65-67, but a patient buyer can still find a good one. Yours appears in great shape, much better than average for 1964 I'd say. Finally, it's an Elsener, not a Wenger, and this will also add to its market value.
I hope this helps,