(Link)
Sir John Seton
1434
Seton Collegiate Church, Port Seton, East Lothian, Scotland
Source - Brydall, Robert. 1895. The monumental effigies of Scotland, p. 409. Glasgow: Society of Antiquaries of Scotland.

(Link)
15th-century effigy of a knight
In 1434 Lady Catherine Seton built a side-chapel to house the tomb of her late husband, Lord John Seton.

(Link)
Seton Collegiate Church
The Presbytery also contains two effigies - an unknown Knight and his lady.
"We do not know which of the Seton family built the tomb nor the identity of the effigies. They may not even belong to the recess but could have been brought from the chantry chapel, demolished in thr early 1500s." Historic Scotland Official Visitors Guide.
"It is possible they represent Sir John Seton and Lady Katherine." Historic Scotland Official Visitors Guide.

(Link)
Cockenzie and Port Seton is a unified town in East Lothian, Scotland. It is on the coast of the Firth of Forth, four miles east of Musselburgh. The burgh of Cockenzie was created in 1591 by James VI of Scotland. Port Seton harbour was built by George Seton, 11th Lord Seton between 1655 and 1665.

(Link)
When Sir John Seton died in 1434, his widow, Lady Katherine, had a family chapel added to the nave, where the tomb was placed as well as an altar.

(Link)
John (Seton) Laird of Seton (abt. 1370 - 1441)
He must have died prior to 1434 as the estates of Seton were in ward in 1434. Maitland, while also getting the date wrong, says he was buried in Seton Church "in the yle foundit be his moder". This is incorrect, as the "yle" was built by his wife, and for him after his death.

(Link)
John SETON (1373-1430)