Was discussing the old Ascot Heinz Chase meeting on X earlier today. Checked the 1969 meeting which I went to and the going was ‘Firm’. The Heinz Chase had 9 runners, the accompanying flat races had 11, 20, 4, 20, 9 and 21 runners.
Similar experience when I first visited Musselburgh in 1993 (then called Edinburgh). Going “Firm”, field sizes 12, 15, 7, 17, 7 and 13.