American Machine-Made Marbles gives this result from a count Alan B made of 470 Peltier comics, suggesting Koko is the least rare and Kayo is the most rare:
Koko: 61 in 470
Bimbo: 58 in 470
Emma: 49 in 470
Annie: 37 in 470
Herbie: 36 in 470
Skeezix: same
Smitty: 34 in 470
Sandy: same
Betty: same
Moon: same
Andy: 32 in 470
Kayo: 25 in 470
And then there are the specialty marbles: Tom Mix, Cotes Master Loaf, Hoover for President, Franklin Roosevelt & Babe Ruth.
Are you sure you had an original Cotes marble? I think there might be some modern reproductions. Maybe? [Edit: yes, there are modern marbles with a Cotes logo on them]