The "Ulster" tartan is very modern, but based on an ancient one.

In 1956 a farm labourer in County Londonderry excavated some fabric out of an earthen bank. Antiquarians and scientists dated it to the early 17th century, and in 1958 a reconstruction was produced on a hand loom. It was registered in the 1970s with the Scottish Tartan Society as the "weathered Ulster tartan" (WR 1196, right) and later a restored version in the probable original colours was registered as the "red Ulster tartan" (WR 792, below).

The "weathered Ulster tartan" was subsequently adopted as a military tartan by some units with Irish connections.



http://www.regiments.org/tradition/tartans/ulster.htm

Sherry