What you have is the fine patina after years of use. That's the surface accumulation of everything that the frame has been exposed to after all these years that gives old things that old "look". Removing all but the surface dust isn't usually all that necessary.

When working with old "stuff" in a museum, the first rule is to do no harm, and I apply that to my old "stuff". We use a soft brush (even a soft, clean, paint brush will work), and that's it! Rubbing with harsh chemicals and abrasive items is anamatha! You can even destroy the value of something by over-cleaning it. The next thing we MIGHT use would be distilled water on a soft cloth and a VERY gentle hand - NO rubbing, just dab....

If the frame has been exposed to years of cigarette smoke, it's most likely nicotine that's covering it, and beyond stripping, it's nearly impossible to remove. That and old varnish or shellac finishes will get sticky when exposed to heat and humidity after lots of years, and it then becomes a dust magnet.

Unless you are willing to strip it completely and have something old look like something semi-new, and possibly destroy any value, I'd just leave it to the light dusting. If it's completely disgusting, then I guess you could do nearly anything to get it to whatever "look" you like.

-Grainlady