How To Date Newer Esoterica Tins?

[badbriar]

I've read all of the older (through 2018) info on dating Esoterica and Germain tins and that made sense. Now, with the later, newer tins that have four numbers before the letter, how does that calculate?
ex. Dorchester tin with code 1359H042.
Before, with three numbers before the letter, the 1 would correlate to 2021 and the month/day - April 2. So it would have been dated as 04.02.2021.
The other method I've seen is that the letter is the number of years, beginning with 2016. This does not work, as this tin from presumably 2021 would be made in 2023 in that case.
Thoughts?

 

[FurCoat]

I've always used the letter method and it's always lined up with the purchase year. The first method doesn't work either. The 1 could be 2021, 2011, 2001, 1991 and so on.

 

[monty55]

@pipestud would know!