How Far Back Can We Go? Seventh Edition!

Excellent examples!

I guess the valid point is that unless the coin is dated, we can find different avenues of scholarship that lead to different conclusions.

Witte attributed the type posted by spence (I also have one) to a monetary convention between Brabant and Flanders in December 1339. Elsen also still cites the date 1339 (for both W. 359 and W. 360).
The 2019 paper found by j1m says only the type with a different legend (GAND LOVAN) should pertain to the 1339 convention, but that type is typically attributed to Flanders, not Brabant: https://www.acsearch.info/search.html?id=4850157 . This is probably the reason W.359-360 continue to be attributed to the 1339 convention.
I dont have time to read all the details in the article right now, but the attribution of the GAND LOVAN type to Brabant may be a potential flaw in the logic (not to mention they repeatedly mis-number the Witte types as 259-260 intead of 359-360).

Anyhow, the supposition of 1341 and 1346 emissions of the John III leeuwengroot still appears to merit consideration since the type persisted to the next reign.

As for the Numista listing it was created a long time ago, and needs some editing. The 1337 date line appears to be incorrect for the type MONETA BRABAN. Probably it should just be 1339-1354 with notes on the dispute in the literature.

Unlike the 15th century, there are no surviving mint records from this period in Brabant, so who knows with certainty exactly when the coin was struck (1339? 1341? 1346? or 1339-1354?).

Not me.
(Note: last edit of these comments 10 a.m. EST on 5/26).

I know practically nothing of this coin type, however, up until I read the academia.com article, I believe that there was a level of agreement that the applicable reference works were Ghyssens, de Witte and Elsen. Lacking any real substantive documented evidence to the contrary, the numismatists of the world have used the dates provided by these reference works as the benchmark.

I base my assertions on the lack of substantive documented evidence within the academia.com article as :

The authors of the academia.com article have implied that Ghyssens' works are mostly inaccurate, and this view is based in large part on the following "compelling" information (my choice of phrase, highlighting and emphasis)

"We are not completely sure about the correct, chronological order of all of the sub-types, but based on certain characteristics of the coins (e.g. the central lion), some sub-types can be placed before others with a relative degree of certainty." I would have thought that to debunk a theory, one would need 100% certainty.

"We have put them in the order that we believe is correct (subject to change based upon new information, should it become available). " As did the others before. (I am still waiting for the "voila" moment)

"It is difficult to determine exactly when many of the Brabant coin types (including the leeuwengroten) were struck". Understandable.

"The coins were first minted in Flanders (sub type mentioned), or perhaps in Brabant." Self explanatory

"We are left to rely on Ghyssens to some extent, although his works must be taken with a grain of salt." Why must Ghyssens' works require seasoning after relying on them to some extent regardless?

"Unbeknownst to Ghyssens, his basic catalog of the Brabant leeuwengroten was flawed, and he was therefore unable to create a completely accurate time-table. "
(1) In what way, pertaining to the dating of Spense's example, was Ghyssens timetable flawed?
(2) viz a viz his timetable must have been somewhat accurate.

"The other Brabant types do not fall within our area of expertise, but as far as the leeuwengroten are concerned, based in large part upon minting of this type in Flanders, we feel that the following is likely to be correct:
Again, this does not instill a high degree of confidence in me.

Until the academia.com article is proven correct beyond doubt, it is not in my opinion reason enough to totally abandon the dates and date ranges already in existence. If and when proven accurate, by all means the new information must be taken above those of the past.
As for the December 3, 1339 dating @Spense's coin, I would have thought that it should be taken as 1339, regardless of whether and or how far it ran into 1340.

Taking a breath, all of that being said, I totally agree with @january1may that the different schools of thought have created a great deal of confusion. I am not advocating that we should take the 1339 date as gospel, but I am saying that those who are familiar with the coin type, should perhaps give their view on whether we should accept the 1339 and move on, or if we should wait for another example of the year to be presented. I would be happy to accept any counsel.

I think @Spense should voice his opinion, certainly. As should anyone else who has an interest and an opinion to share.
@tdz has already added some thoughts which I think are aligned with mine, but that would be for @tdz to clarify.

I put my feelings down because I thought it quite strange that an article could be so definite and disparaging in its contrary views while being prefaced on perhaps and we feel it likely etc. What do others here think of the article?

It seems like the consensus is to accept and regress to 1338/738.

Anyone opposed? I welcome the opinion.

Sounds like I can post this 1338-datable Hungarian Denar (Frynas H.24.26; Huszar 495):

AH 737 1337 CE Dehli Sultans 6 Gani