Surprisingly (to me) they make reproductions of these, for reasons described here; Amazon.com: U.S. Browning M2 Tripod .30 Cal Brass Data Plate: Everything Else
Other than that, it's off off just what it says on it. Yours correctly has the comma after "mount" (so correctly read you know it's a tripod mount) rather than the repro shown in the link. But their description of the history on these was interesting enough to have it included here (if correct).