I'm in need of advice here, this bag has been collecting some serious amounts of dust for the past 80 years and I'm no expert on preserving leather or the like. But the dust is fairly engrained into the leather giving it a matte grayish look which is fairly undesirable to me. I am worried about using water on the leather as I have made some mistakes with other older leather resulting in it becoming very brittle and just falling apart. The canvas is also fairly stained and pretty stiff, id there any way to remive the stains and rejuvenate the canvas? I appreciate any advice you'd have on how to clean and preserve this bag thank you. 

I see the mottled look you are talking about on the leather. I wouldn't think dust could actually work its way into leather but perhaps it could. Otherwise, I'd expect it is just the effect of aging or contact with other elements. Two products often mentioned here are Renaissance Wax and Picard's Antique Leather Treatment. There are certainly a different thoughts here as to the pros and cons of each but I've used them both and am happy with the results. The "Ren" Wax is a bit pricy though. Nice bag though so best of luck.