I am looking at a trade for my Colt OMM .22. I don't know if it is single action only from the factory or if it was done later. I saw some pictures somewhere on the web but still wasn't able to decide. Does anyone know an easy way to tell? The serial number is 673XX. Thanks.

Factory SAO OMM's were a special order item and very scarce. Only a Colt Archive letter will tell you for sure.

Only ones I know about were SA/DA. It could easily have been converted to SAO by a former owner, just as an S&W can be by removing the hammer's DA fly (Colt called the same part the "hammer strut"). Check for its presence or absence on the hammer before you go sending for a letter.

There are ways to tell, hopefully someone will be along to help. These are Colt factory photos showing the two actions, I’m assuming the bottom one is the single action as my double action OMM cocks like the top revolver he’s holding.
Regards,
turnerriver

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turnerriver

I'm assuming the bottom one is the SAO? Thanks. Great pictures.

By the way, my cylinder rotates even though the hammer remains silent. Would that be true if it is a factory SAO?

Mine cocks like the top one. Thanks. And I just remembered why I bought a new camera! Hopefully I can post decent pictures.