David Pickett Antiques has dated this piece to the 18th Century.
Both have false bottoms, copper bases and visible seams under the handles.

The tankards are in good condition with some copper bleed to body and tops of handles. The larger tankard has a slight ding to the base and the smaller tankard has a stubborn black mark to the side. Both tankards are watertight and have relatively clean interiors for their age.

Large tankard - Height to top of handle approx 16.5cm. Base diameter approx 11.5cm. Weight approx 510g
Small tankard - Height to top of handle approx 13cm. Base diameter approx 9.5cm. Weight approx 354gg
David Pickett Antiques has dated this piece to the 18th Century.
Specialists in old sheffield plate
You can view the stock and full dealer information on the David Pickett Antiques Profile Page