Magnifying lens attachment for bull's eye lamp

Magnifying lens attachment for bull's eye lamp
Object name 
Magnifying lens attachment for bull's eye lamp
Date 
1850-1860
Medium 
Glass, pewter
Dimensions 
Overall: 1 1/2 x 3 7/8 x 3 in. ( 3.8 x 9.8 x 7.6 cm )
Description 
One round convex lense in pewter frame with shade.
Object Number 
1956.175
Marks 
stamped: on frame: "Patent"
Due to ongoing research, information about this object is subject to change.