I'm seeking to get a better understanding of what the early forms of plate augmentation for the arms and legs that developed in Europe in the late 13th century looked like. What are some good manuscript illustrations or surviving peices to get a sense of what of early "partial plate" armour looked like?

Plate leg defenses appear earlier. One of the earliest references for enclosed greaves appears in the 1302 Inventory of Raoul de Nesle, the Constable of France killed at the Battle of Courtrai.
Item ii harnas de gaumbes fourbis de coi les greves sont closes cs.
Item, 2 leg harness polished with enclosed greaves. 100 s
Item unes autres demie greves fourbies iiiil.
Item, one other half-greaves, polished. 4 l.

Unfortunately the words used to describe these defenses (schynbalds, jambiers, trumelières, etc.) don't explain their appearance.

---

 Attachment: 16.46 KB

Apocalypse, Toulouse BM MS.815 fo.27v, 1220-1270

 Attachment: 158.33 KB

Trinity Apocalypse, Cambridge MS R.16.2 fo.23r, c.1250

 Attachment: 48.96 KB

'Goliath', Maciejowski Bible, Morgan M.638 fo.28v, 1240-1250

 Attachment: 55.73 KB

Lambeth Apocalyspe, LPL MS 209 fo.11v, late 13th century.

 Attachment: 78.21 KB

Cathédrale Notre-Dame de Paris, 1214-1270

A rare example of some possible forearm and shoulder plates.
http://manuscriptminiatures.com/4345/18978/
[ Linked Image ]

Effigy formerly attributed to Sir William Longespée the Younger, (+1250 Battle of Mansourah), Salisbury Cathedral. Sometimes dated 1250-1270, now listed as an "Unknown 14th century warrior" due to "recent research".
[ Linked Image ]

Simple roundels or cups over the elbow are usually the most plate on the upper limbs found in thirteenth century art.

Supplemental leather defenses over the mail should also be considered.
http://armourinart.com/169/261/
[ Linked Image ]

Plate-lined surcoats were also appearing mid-13th century.

Matthew