To see all files attached to order use:

svc=order/list_attachments&params={"itemId":<long>,
				   "id":<uint>}

[
	{
	    "n":<text>,		/* file name */
	    "s":<uint>,		/* size, bytes */
	    "ct":<uint>,	/* creation time */
	    "mt":<uint>		/* last modification time */
	},
	...
]