The croccia with its Renaissance sheen and rich color is an interesting garb that was sadly done away with in the sixties. In the photos can be seen the summer and winter versions of the croccia. It is difficult to find info in English on this now mostly forgotten tradition. For the Coronation Mass the men who carried the miter and tiara were vested in the croccia.
Below is an explanation from our Polish friends, found on their excellent liturgical site here. "The croccia was a special garment to which the prelates di mantellone were entitled. It was put immediately over the cassock. It comprised of a long robe open at the front, fastened at the neck like the mantellone, with two capes: the outer one which was shorter and the inner one – which was longer with a hood. In the summer version the capes were made of scarlet silk, contrary to the rest of the robe which was woolen. The exceptions were the sleeves with the lining and trimming which was made of amaranth silk. The croccia was used in the Papal Chapel and during the consistory and also outside Rome in the case when a given prelate fulfilled the function of a special papal delegate (e.g. when giving the biretta to a newly nominated cardinal abiding outside of Rome)."
There are different versions of the croccia that were worn by different priests and prelates of the Papal Household. For more information with photos, see here.
The winter croccia:
