This P&B Wools (SC44) Quickerknit baby book was sent to me by Geraldine in the UK.

Quickerknit Baby Wool is described as “thicker than 4-ply and finer than double knitting” – evidently double knitting was not thought suitable for babies, but this would knit up more quickly than 4-ply. Thanks to to Barbara at barbaraknitsagain for the information.