This is the "variant" type of sign in that it is not Keystone shaped, and are often found, as does this one, to mark "Borough Lines." Note this one is not on a front mount post, as are most, but rather on a replacement piece of round pipe. We do not know if these were part of the Dept of Highways program or whether they were obtained by the boroughs. As there are several in scattered parts of the state, there must have been some centralization to them.
Zinns Mill Road