RAMANAM
In the Name of The Father, and of The Son and of The Holy Spirit, Amen.

The existence of codes in both OT and NT has been an assumption or a knowledge for as long back as I am aware of exegetical scholarship.  Knowing what the codes are, however, is another matter. General characteristics are known, but details of the actual codes get lost over time.  And with the losing, interest flags because except in the case of a serendipity, reacquisition of the codes is almost always merely speculative.

Some of the lower-level codes are used by an American or Britisher who wrote the first pro Baha’i book here. I forget his name, but his use of codes to figure out the “years” of prophetic dating is quite good in the sense of accurate, in my opinion.  He may have been William Sears.  Baha’u’llah gave out some of the codes and his son’s published exegesis contains some of the results.

There is also this, take it for what it is worth.

Ashkenazy Kabala is based on the presence of OT codes, but it is not systematic or self-agreeing. Jerome reports some codes, approvingly, especially with respect to the Psalter, which is the guts of both OT and NT. The last book of the NT is all code, but I don’t know anyone who knows the key. It’s just that there the code is pretty clearly exposed to view as code. Usually it is more sequestered.

AMDG