In Angelus Milling Co. v. Commissioner, 325 U.S. 293, 65 S.Ct. 1162, 89 L.Ed. 1619 (1945), the Court held that the claim was untimely but stated that a waiver might be found where "the evidence is clear that the Commissioner understood the specific claim that was made even though there was a departure from form in its submission," and "the showing is unmistakable that the Commissioner has in fact seen fit to dispense with the formal requirements and to examine the merits of the claim." 325 U.S. at 297, 65 S.Ct. 1162.