This item is currently for sale on ebay. It is described as a 'barrel tool', but, I would think it more likely an ammunition gauge, given the "Frankford Arsenal" marking.

It is dated "1905 J.M.G." (or J.M.C.) and one side is marked 'MODEL 1898' and the other side is marked 'MODEL 1903'.

IMHO it must have been used to check certain dimensions on .30 U.S. Army cartridges (.30-40) and .30-03 Springfield cartridges.

Any thoughts or answers?

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