[Klaus]

Here we go then ... https://www.tamron.jp/en/product/lenses/a071.html

[Brightcolours]

Confusing stuff from Tamron: They introduced "Di" to their lens names to communicate that the lenses had improved coatings to counter the heavy purple fringing that popped up with digital SLRs, Di meaning (nonsensically enough) "Digitally Integrated". That is right, the lower case "i" stands for upper case beginning "Integrated". And "Digitally Integrated" means... better analog coatings on the analog glass back element.

So far, so "good".

Then they started to design lenses for the smaller APS-C sensors, lenses with a smaller image circle (because of APS-C only) and more fitting focal lengths. They decided to give these lenses' names the "Di II" addition, signifying that these lenses were for APS-C cameras (DSLRs).

Then, Tamron decided to develop lenses for MFT. They gave these new lenses' names a "Di III" addition. MTF was the 1st new mirrorless format (Leica M went before).

So, Di stood for FF, Di II for APS-C, and Di III for MFT.

Enter the rising popularity of other new mirrorless FF and APS-C platforms. Tamron has decided to name all "mirrorless" lenses (I mean lenses for "mirrorless cameras") "Di III".

Di : full frame DSLR lens
Di II : APS-C DSLR lens
Di III : MTF lens
Di III : APS-C mirrorless platforms lens
Di III : FF mirrorless platforms lens

What actually is quite impressive about this lens, the focus breathing seems to be less than what is usual for its ilk.