Dr. Diener working on 15-30 tags!

I'm not sure quite yet what order it's in his schedule, and not likely available until this fall, but Dr. Diener has started work on 15-30 tags!

This is a tag [on a tractor in my area] discussed here earlier:



Obviously this tag speaks for 1929 and I have to guess at least '30 and '31, as well as several years before [with 15/30 HP and 1000RPM]; '29 +&- a couple would be 75% of the production anyway.

Does anyone know if there are any varations [serial tag, not tractor] aside from the HP and RPM update of 1929? I've heard the late ones may have had a tag completely different, but well out of my knowlege when, or if this change occurred.

Is it correct to guess that this tag was used all the way back to the first 15-30s? If not, any idea how early and what differences there were?

BTW, I have a sample of a Farmall tag from Dr. Diener; I'm not always as tuned to details as folk many here, but the difference is night and day sitting next to a cheaper version sold online!
Truth be told, having not seen the difference in quality and attention to detail, I would have likely been quite satisfied with the other one, but after a T-Bone, round steak just doesn't seem as satisfying.

Hijacking my own thread here:

Does anyone know what the two holes above the tag were used for?

Check the backside to see if there aren't two more corresponding holes being covered from the front by the serial number tag.

My tractor, the neighbor's tractor, and the one in the photo, all just had the two holes corresponding to the tag and none hidden by it. There are the two holes above it though that still have me scratching my head.