Hello I come from the land of tool collecting.  I don't know if you'll find this interesting or not. But I'll post in case someone does.

I bought this rule a couple months ago.  I got curious and started researching who J.S.Adams was. After a couple false starts I have landed here.  I am now almost certain is J.Sumner Adams's machinist ruler.

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The front of the rule. The D&B Stamp refers to Darling and Bailey   Samuel Darling and Edward Bailey partnered making engine graduated machinist rulers from 1852-1853 in Bangor Maine. Of course we know that J.S. Adams was living in Seco Maine at the time.  Young J.S. Adams would of been 14 years old, the common age of an apprentice at this time.

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The back is very interesting.  We have the stamp J.S.Adams!  Either very nicely done or a custom stamp.  Both a sign of an skilled or accomplished machinist. If it was custom, surely it must of been used else ware. Anyone see it?  Moving to the center another small "J.S.A." stamp.  Looks to be double struck.  On the right.  Just "SA". No J. The S is faint. the A looks like its been triple struck. Looks like work of an young apprentice.  For whatever reason J.S.A. didn't like his first name.  He is even listed in the 1850 census as Sumner J Adams. So,  I think he would of had the ruler since he was an apprentice.

Thanks AFJuvat and butlersrangers for the posts on J.S.A.  Without the posts and pictures, I may of never figured out who J.S. Adams was!

What a find! I wonder if anyone outside his family knew what they had before you discovered it?