Wiktionary
n. 1 (context now rare or historical English) Either of the lamps on either side of a gig carriage; a headlamp. 2 (context in the plural dated English) spectacles.
Usage examples of "gig-lamp".
But his broad face, dominated by that great brow, was flecked with sweat, and his eyes, made small by his thick gig-lamp spectacles, danced and gleamed.
Even now he was taking command of the situation, stalking back and forth beneath the hovering ball, peering up at it through his gig-lamp spectacles and scratching his chin as if he were as sage as Newton.
You might see his bay-mare and gig-lamps a score of miles away from his Rectory House, whenever there was any dinner-party at Fuddleston, or at Roxby, or at Wapshot Hall, or at the great lords of the county, with all of whom he was intimate.