WOw what a cool vintage bag congratulations! Im not sure which leather you have either.. it kind of looks similar to Gulliver or Evergrain or even well used charmonix but no matter

Well at this point seeing how much of the discoloration you see is actual wear with color loss...and you like the look correct? Then I would just go over it gently on the back of a strap or some other hidden spot as a test area with a soft pink eraser and see if any dirt comes off... be very careful and make sure you aren't removing the finish when you do so. If you are actually lifting off surface dirt continue to the rest of the bag's panels. Then have a look.... now you can choose a leather cleanser use a proper leather cleanser and not a leather cleaner/conditioner product. Then after its dry have a look. Is this the look you want? If this is not the look you want , then do not condition at this point you will want to have the bag professionally color restored. However if you like the look and you are good with the over all look you can condition with a cleanser/conditioner or a light non greasy non waxy type conditioner, a lotion type would be a good start. There are many good light leather lotion conditioners to choose from and lots of good companies who produce them. You can go to your local cobbler and see what they have on the shelf . or try google or
amazon or ebay search boxes. Meltonian , Woly, Kelly,saphir etc... all make great products
However I would stay away from saphir renovateur and any other very greasy conditioners on this project because your bag has so much missing finish and top skin rubs.. using greasy and or waxy products will make the worn areas darker still and I doubt you would be happy with this result.
Lets see how it looks after the cleaning OK? Good luck!
doc