I had previously made a post which indicated that Jacob Seybert's German signature - Jacob Seibert - found in two probates - that of Mark Miller (1757) and Henry Lawrence (1758) did not seem to match that of the immigrant, Jacob Seibert, aged 28 yrs, who arrived in 1738 on the Glasgow.
However, a third signature of Jacob Seibert was located on the Zorn probate (1755) and it is very similar to that of the 28 year old immigrant on the Glasgow.
(All three probates were digitized by Eric Hedrick in his collection of Historical Documents from Augusta Co. Each signature is on what appears to be an original document which bears traces of the red wax seals).
It is now not clear - to me - whether there were two Jacob Seiberts in the South Branch basin for at least a short time or whether one Jacob Seibert's signature deteriorated rapidly (in the space of a year and a half). Normally, it could be said that two men of the same name might be a stretch but we know that at least three men of the same name and from the same area (Saarland) - and closely related - arrived in 1738. One of those three was illiterate and did not sign the Oaths lists and a third did not sign either because he was too young or for religious reasons.
With three Jacob Seibert immigrants of the same region and near the same age, it's a good bet that there were others both older and younger - whether any immigrated or were born in PA needs to be worked.
There is no quick resolution to the problem and the answer may require research in Pennsylvania. I will be working on the problem but would appreciate any help - particularly with other samples of signatures of any Jacob Seibert between 1730 and 1770.
I collapsed the old post to avoid further confusion.