The serrations are on the front of this old Colt

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The serrations are on the front of this old Colt
From Top to Bottom:
Colt M1902 Sporting - .38 ACP Colt M1911 A1 - .45 ACP Colt M1903 - .32 ACP Colt M1908 Vest Pocket - .25 ACP
Colt M1902 - .38 ACP
Colt M1902 - .38 ACP
Colt Model 1902 - .38 ACP
Before there was a Colt 1911, there was the Colt 1902 "long slide" pistol. Don't be fooled by Colt's name though, they were both designed by Browning.
(via https://www.youtube.com/watch?v=URv_q2NxbCU)