The only track I can think of for which Curr became known (other than his regular plateways) was that used in Sheffield along Duke, Broad and South Streets carrying coal from the Duke of Norfolk's collieries in 1776. The line was approx 2 miles long and used shallow flanged rails 6ft long, 3" wide, with a 2" high flange. These were secured to wooden sleepers (4"x2.5") placed every 6 feet. The rails were rolled by Joseph Outram (Benjamin Outram's father) at Ripley Ironworks (Butterley).
This is the only out of ordinary Curr product I can think of but not sure it was narrow gauge! Curr was apparently influential in Coalbrookdale and narrow gauges were used there... perhaps using his 6 ft long rails.... though I can find no ref for that... sorry.
Regards ICLOK 😉
Aaaaaaaaaaaaaaaaaaagh Creeper!!!!!