From Pebble pattern book (1960s):

“Pebble is rough-grained, racy and rich - it’s quick and easy to knit. It’s a great look: tweeded and textured…Patons Pebble is a moth-proofed, pure new wool knop yarn with an interesting tweedy texture, in basic colours flecked with contrasting shades. Being a ‘soft spun’ yarn with bulk, it is pleasant and quick to knit. Patons Pebble has qualified for for the Pure New Wool Symbol of the Australian Wool Board. This symbol guarantees that Pebble is pure new wool and that it meets performance standards set by the Wool Board.”