Searching for a marriage record from Dec 1777 at "Hospital Johänis" in Mainz, Hesse, Germany

Question

I'm looking for the marriage record of Gottfried Schneider and [Joanna] Anna Maria Schwabel, who were married in Mainz, Germany on 10 December 1777. I know the date from an index, which lists the place as "HJ," or "Hospital Johänis." My best guess is that this was a chapel in a military hospital (https://www.regionalgeschichte.net/rheinhessen/mainz/einzelaspekte/die-geschichte-der-krankenhaeuser-in-mainz.html#c89866), but I have been unable to find any information or records beyond the index. I am unsure if Gottfried was part of the Hessian military at the time, as I have not found any records indicating that he served

Here is the index image on Ancestry, with a transcription:
https://www.ancestry.com/imageviewer/collections/7506/images/41518_kkmz0000000186-00855

Here is the same index image on FamilySearch, without a transcription: https://www.familysearch.org/ark:/61903/3:1:3Q9M-CSDB-293H-K?i=6981

Answer 1

On matricula and archion are no church records from Mainz online avaible until now. Some military church books from Mainz are online avaible, but they start 1851.

Answer 2

Just wanting to add to what Dieter Lewerenz said.

According to this site (search for "St.Johannis-Hospital"), baptisms and marriages from 1779 and later are available at the Dom- und Diözesanarchiv Mainz. According to this site (search for "Archive), many church registers from before 1798 are kept at the Stadtarchiv Mainz. The same site (search for "St. Johannes, Hochzeiten") also indicates that marriages from the St. Johannes parish from the 1698-1796 period are available at FamilySearch, however St. Johannes and St. Johannis-Hospital may not be the same thing.

J

Comments

PS: Let me add that Schwabel doesn't seem to be a common surname, whereas Schwebel (phonetically very close to Schwäbel/Schwaebel = Schwabel with Umlaut) is more widespread.

J