1917 27 Nov. 1/4 Lucky? I'll say so. All that long wait has turned into mighty good fortune, I think.
1929 H. V. Morton ii. 46 ‘You have seen the Crown Jewels in London?’ ‘I'll say so! They're an eyeful.’
1992 C. Toibin (1993) viii. 103 ‘You'll probably come back with your father.’ ‘I'd say so, all right.’