Hello,
I've got a little problem. There are some leather limb protections on Italian iconography from 13th century. But I haven't found anything like this made for a trunk - everything here is covered by armour cloth. Does any of you know an armour (coat of plates, leather) used by Italians to complement their chainmails?

That's a fairly common problem for all of Europe in the 13th century: The body armor is hidden beneath the cloth surcoat. Italian art is doubly called into question because of its continued depictions of "Roman" features such as pteruges over the upper arms and hips. Is this early 14th century example a realistic depiction of leather over mail or an outdated artistic convention?
http://manuscriptminiatures.com/4675/9174/

There are surviving documents, but translation and correlation of armor terms to images is difficult if not impossible. The Societa Dei Lombardi in Bologna passed this rule in 1256:

Quote:

XXXXVI Item statuimus et ordinamus quod quilibet de societate armorum debeant habere scutum seu scrimetum, elmum vel caçetum, cubam vel guayferiam vel lamerium cum insignia societatus intus, et eam, portare in dorso in Omni exercitu et cavalcata et strenuta.

The choice of body armor among cubam or guayferiam or lamerium exists, and some authors have suggested the latter to be a pair of plates. I don't know if we can accurately correlate any of them.

"lamerium" looks like a variant of "laminis", which Gerald used to describe the armour worn by some of the Danes during the attack on Dublin castle. I don't think it is possible to determine whether it is scale, lamellar, or a COP.

as a re-enactor from Italy I'd quote everything above... to state the obvious it's generally acceptable here for 13th century groups (particularly in the 2nd half) to wear leather semi-rigid protections above the mail (as knights) or above the gambeson (as infantry)