The Buchanan name is connected to the lands surrounding the eastern shores of Loch Lomond. Buchanan is a clan tartan and it is available in several versions, of which the antique one shown here may not be one of the most typical Buchanan tartans.
The Buchanan kilt was one of my very first ones and I bought it online from a no longer existing kilt shop in Glasgow. Lightweight PV it is and approx. 4 yards.
The Buchanan tartan provided by USA Kilts for their casuals will come rather close to this one, as far as I'm able to tell, whereas the Buchanan Weathered tartans offered by KiltSociety, Heritage of Scotland, and Scotweb all look different.