1) A doubler was a large plate or dish, and examples of the word occur from the 1300s (OED).
The dishes could certainly be made of pewter but wooden ones are also on record: 1546 one wood dubler, Leeds
1585 4 cheesefattes, a wood dubler, a chirne, South Cave
1592 4 boules, 4 treene dublers, South Cave
1638 one kit and a wood dubler, Thorpe Willoughby. In an undated deed, probably of the thirteenth century, Hugh le dublerwrith was said to be living in Adwick, a specialist wood-worker, so perhaps the article was usually made of wood in that period.