I have a Remington single shot 32. rifle with octagon barrel. Serial # J187134.
Does anyone know when it was built?

Are you sure there isn't another letter with it? The site I use requires a two or three letter prefex. The first letter will denote the month, the second letter the year. 'Course, it could be that what I'm using doesn't go back far enough too. Sorry.

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"It is the province of knowledge to speak and it is the privilege of wisdom to listen". Oliver Wendell Holmes

I've seen the charts stating there should be two to three letters. There is only one.