Last year I got a sword in my possession, in a very good condition (indoor patina) with a scabbard whose leather shell unfortunately falls apart in VERY little pieces. 
A round pommel, actually a basic shape, Oakeshott type R, rarely used on swords, when.... mainly on  Scottish and Northern European swords. 
a stiff diamond-shaped blade for the thrust and a hilt with inner and outer rings, wide parry rods with saucer-shaped finals.
long leather bound grip with two rings at each side.
the sword's is 142.5cm, blade  102.5cm.
in a plastic folder to parry ring was a piece of parchment with family crest at one side and a written part at the other side.
I have found that the text on the old parchment must be;
Two handed sword used by David Stuart of Inchbreck  with which he killed the Earl of Huntly at the Battle of Corichie  fought on Oct 28th 1562
the weapon on the other side is the family crest of the Family Stuart.
Motto: Semper apparatus = Always prepared
Blazon: A Civet Cat Couchant Ppr.
SourceFairbairn's Book of Crests, 1905 ed.
Because the weapon of Stuart of Inchbreck it is depicted on the parchment , in all probability, made up by someone from the Stuart of Inchbreck family. 
when, I don't know.
I found in Bernard Burke, 
A genealogical and heraldic history of the landed gentry of Great Britain & Ireland volume 2 page269,
the existence of an David Stuart corresponding to the event.
Xiineag-e.— David Stuart, first of Inchbreck (1547), was 
 son of Andrew Stuart, of Johnston, or Laurencekirk, in the 
 Mearns, and grandson of Sir James Stuart, of Athol, son of 
 ilurdoch, Duke of Albany, who was grandson of Robert II. King of Scotland. 
in practically all documents state that the Earl of Huntly is deceased to internal bleeding or stroke after he was captured in1562.
However, in
William Ruxton Fraser , History of the parish and burgh of Laurencekirk is written about the incident, the stabbing death of the Earl of Huntly by david stuart.
http://www.ebooksread.com/authors-en...kirk-ala.shtml
REDMYEE. 95 
his death; and in a retour of 5th May 1658, there 
 is mention of " Alexander Irwing of Drum, heir-maill 
 of Alexander Irwing of Drum, Knight, his father, in 
 the lands of Whytrygs and Beidmyre." It was prob- 
 ably this Alexander who disposed of the estate to 
 one of the family of Stuarts. 
It has been said, however, that the Stuarts of Inch- 
 breck acquired possession of Eedmyre by marriage, 
 though the time of its coming into their hands is not 
 known. According to Mr Jervise, the first Stuart of 
 Inchbreck was a younger son of a laird of Johnston, 
 who was a lineal descendant of the old family of the 
 Stuarts of Morphie. David Stuart fought at the 
 battle of Pinkie, and was of invaluable service to 
 Sir Archibald Douglas when he lay wounded upon 
 the field. For his attention to the knight, he was 
 rewarded with a gift of Inchbreck, which had been 
 part of the barony of Glenbervie. He continued to 
 distinguish himself as a soldier, and was with Queen 
 Mary's forces at the battle of Corrichie, where, it is 
 alleged, he killed the Earl of Huntly with his own 
 hand, a feat celebrated in the lines of the old ballad : 
" The Murray cried, 'Tak' the auld Gordoun,' 
 An' mony ane ran wi' speid, . 
 But Stuart o' Inchbraick had him stickit, 
 And out gushit this fat lurdanes bleid. "
very nice that an old ballad refers to the death stabbing of the Earl of Huntly by Stuart of Inchbreck.
family fantasy of the Stuarts for by the fire or real truth, whether or not the sword where Earl of Huntly was slain along.
who knows?
certainly very interesting and entertaining
best,
Jasper