Heroes of Might & Magic 3 adventure map object reference
Solution 1:
An authoritative source for this information has been identified as the HoMM3 map editor. Right-clicking on an item in the object selection tab brings up a tooltip containting this info.
Solution 2:
All the reference information and much more you can find here: http://homm3world.narod.ru/ (FizMiG menu item on the left). But this document is in Russian.