what is a silver antique brush comb and mirror set worth?

Depends. Who made the set ?? Their markings should be near the spot where the Stirling Silver mark is. Unfortunately, these sets are a dine a dozen…….and a pain in the as* to keep clean, so they are not as sought after as other collectibles are……hence their value can be rather low. Having said that, if the markings indicate they were produced in limited quantity by a very rare artist, then you could conceivably have something worth a few bucks……….best bet is to bring them to an Antique Dealer and get them appraised.