Graeme, the second images is Plate #38 from Worcester Junks and Sampans of the Yangtze.

Yes, the rig has evolved, both in Asian countries and when it was matched with Western hulls. That's typical for good ideas when needs and materials change. And since it is a relatively rare and specialized idea, its evolution has been driven by just a few individuals who have chosen to invest their time and resources and have generously shared their results.

Tom Colvin was one of those individuals who unfortunately died somewhat bitter due to the lack of acceptance of his efforts. I was fortunate to have sailed on one of his designs which changed my way of looking at rigs. He was the last bridge to older times having served on commercial sailing ships. His self-published book "Sailmaking" is a valuable resource for sailmaking and rigging and tuning a boat and it is a window into how things were done by sailing ship pros. I feel fortunate to have an autographed copy that I bought from Tom in 2005.

Yard, batten, boomlet, or? A yard is a spar that a sail is hung from. Mat sails, which all junks originally had, were not strong enough to support much of the actual weight of the sail. So the unique solution was to hang the mat sail from a ladder framework of spars and bolt ropes so the weight of the sail was incrementally supported by the yards and boltropes. The photo of the junk with the tattered sail clearly shows this framework supporting the remnants of a mat sail. So the uppermost yard would be called the main yard if the sail was attached to the main mast. The lowest yard would be called a crossjack yard because it supported no sail but was sheeted. The others, who knows - I wish someone had recorded their Chinese names. Call them yardlets? When 11-inch wide weak cotton sail was available and adapted to sea going junks the seams were still made horizontal, mostly, and that weak sail cloth still couldn't support the full weight of the sail so yardlets were still used to take the weight of the sail. With modern high strength sail cloth the seams are run vertically and the yardlets don't carry the weight of the sail but are attached to it. So the yardlets no longer function as true yards. The closest term that I know of that fits is batten. Only model ship builders still use the term crossjack yard. The lowest yard is not a true boom but it does fulfill some of the functions of a boom so I guess it is a boomlet?