That was a serious journey. From what I can tell, while there are a few sites that quote this same text: 1, 2, and a few others I didn't bother saving. I could not find any examples of it in 1600's printers (not painters like I searched for far too long) , though, I didn't check Google scholar. Here's a guy blogging about the topic and some interesting pictures of old watermarks. . This leads me to believe that this particular version of the Cross was... A recent creation.

The best real lead I've gotten is This here which goes over the triple tau cross, and the sigil of saturn which could seem to make up the top and bottom portions.. The tau triple cross is a connects it to the ihs christogram. Whereas the The sigil of saturn has connections to the demon azezal. this furthers or doubles down on the as above so below concept.

This is my own personal musings: Alternatively, this site lists the bottom portion as the alchemical symbol for alembic. which makes sense given the as above so below element of that portion. I suggest that the 4 represents tin and the + is representative of vinegar. Tin (Sn) plus vinegar (CH3COOH) yields Tin(ii) Acetate or Vitriol of Jupiter.. The distillation of τin Acetate is used in various alchemical processes which I'll leave το you το discover. In summary, I believe this to be a Symbolic representation of one step in a larger process, rather than a symbol for worship or contemplation on the icon of Hermes.