Note on Tension:
The stitch called double moss stitch is the UK is known as moss stitch in the US.

Booklet B19 is exclusively for double knitting yarns.

On page 152 of the Family Knitting Book, and page 6 of the leaflets.

Chest 24”-32”. Between 13 and 24 balls (which were 25 gram size).

Hermit Double Knitting wool/acrylic blend was available in 25 gram balls of about 53 metres length.