One artist to consider is D. Rickard who signed the art on three of the first 10 Harlequins (2, 7, 9) and clearly did the covers for two more (3 and 4). Of the remaining four (5, 6, 8, 10) Wolf of the Mesas (6) is likely Rickard's work as well. And one dealer says he did the art on #5, but it doesn't look like it to me. In summary Rickard did five, likely six, of the first ten Harlequin covers.
The man on Harlequin 1 to my eye has some of the characteristics of Rickard's work but it's not as obvious as his distinctive art usually is. But the woman doesn't. One other point is that at least four other Harlequins that are clearly his work are not signed.
Harlequin 1 - May 1949